As people asked me to explain my views on itemsets and what exactly I mean with it, so here comes a massive wall of text explaining why I think seperate itemsets are a good idea, how they would work, what is needed to make them work, and why the current situation is not good.
What are seperate itemsets?
First what is the basic idea? The idea is to seperate items per archetype or per champion. In doing so certain combinations of items and champions will no longer be possible. Certain items would be available to multiple archetypes or champions, and in certain cases one could make several versions of the same item. For example Ravenous Hydra could be made into a ADC version, with high damage, a bruiser version, with lower damage but better defenses, and a tank version which offensivly has very little beyond the active & passive utility but the best defensive bonusses.
There are two rough approaches for this:
The first approach is to simply make a unique itemset for each champion. This is by far the most basic approach, and will result in the best balancing as you can balance each item exactly perfect for each champion. However, it is impractical as in between 100's of champions and 100's of items this'd be quite a lot of work. Especially considering the existing base of champions & items this would be problematic. However once established it becomes considerably easier to maintain and this is no longer of considerable importance.
The second approach would be to make itemsets based on champion archetype. In contrast to balancing each and everyone item for each specific item you merely balance it per archetype. It is easier to establish & maintain as it requires the least amount of effort, however it will also be relativly less balanced due to individual differences between champions allowing for occasional abuse of certain items due to higher synergy.
This second approach also comes in two flavors, first is limiting champions to their specific archetype set. The other being allowing champions acces to every itemset, but once you build something from one set you can't build items from another set, akin to how the current gold items work.
One can also use a combination of both approaches, using itemsets per archetype to broadly balance and further balance the occasional extreme item on a champion specific level. This is most likely the best option in light of practicality and effectiveness. Also, limiting the items to certain sets while allowing all champions acces to all sets still allows for meta-breaking, even if certain items would not be accesible.
What are the advantages & disadvantages of seperate itemsets
Seperate itemsets has a number of advantages
First it allows for items that would be acceptable in certain roles but overpowered in other roles. Support items are a prime example of this. Often support items are lackluster statwise because once they are good other types of champions will start to use them.
For example take Runic bulwark, as a support item, this was perfect. It provides all-round defensive stats, improves your allies, is cost effecient, slot effecient, provides enough MR on its own to be usefull as a tank. And then bruisers discovered that bulwark did not only help your allies, but was actually a good item. And thus everyone started to build the thing. As a consequence riot removed the item, as it was supposed to be an item a support would get to help his allies, not the goto MR item on bruisers. Had it not been accesible to bruisers the item would not have been removed when it was.
Another example would be the spellthief's edge line of gold items. In order to prevent certain poke heavy mids from abusing the item it comes with some severe limitations. It has extremely low AP for its cost, and it doesn't work just after killing a minion.
Itemsets would avoid these issues.
Secondly, it stops certain toxic, or extremely effective itembuilds. For example it stops bruisers from building full tank, yet have considerable damage thanks to 1 extremely effective offensive item. Or glass cannons from tripling their effective health with a single high end tank item. More on this will follow in the section where I go into why the current situation leads to issues.
Third, it allows certain utility items to be possible for different types of champions with more appropriate stats while not being vastly outclassed by the other variations. For example take ravenous hydra again, a tank might want its waveclear, however its stats do not exactly fit in a proper tank build. To a degree this is also possible in the current system, an example of currently existing items that attempt this being the upgrades following on sheen, however the attempts at this are limited because of the potential of one of its variations outclassing the others in virtually situation (e.g. trinity force is used almost twice as much as frozen gauntlet according to lolking indicating trinity is much more effective in nearly all cases)
Fourth it allows for a greater distinction between the classes. Currently bruisers can reach (nearly) the same defenses as proper tanks, while still having a massive offensive advantage. Tanks especially suffer from this early on, without items their defenses are barely higher than offensive focussed characters, while the disadvantage in offense is actually significant. Similarly certain glass canon bruisers can put out ridiculous burst while not being particularly squishy thanks to their inherent protection.
Fifth, it allows for new highly specialised items and tactics with new mechanics to be viable. This point is similar to the first point, however the first point merely focusses on stats. Bulwark was abused because it had decent stats, the actual mechanic of buffing your allies was never a problem because the thing didn't stack. Now imagine a bulwark that provides a MR bonus based on your MR, now take an entire team that focusses on using these kind of support items to boost their stats skyhigh when they are together, but leaving them weak when singled out. In the current stat this is impossible because not only would they be able to boost their stats massivly, but thanks to the other items they get they wouldn't be weak when left on their own.
Sixth, it allows for better balancing of champions. Take for example the AP ratio's on leona. They are so low that any AP is just wasted, however if they'd be increased you could get a mage leona that'd be able to nuke down targets. If leona wasn't able to build say 600 AP, the ratio on eclipse could be increased so that the bits and pieces of AP she can gather from items like frozen gauntlet actually does something usefull on it as opposed to adding a insignificant 12 damage before migitation. Similarly, AP yi would've never been as toxic if he didn't have acces to lich bane or lacked the 900 AP needed to blow up squishies.
Seventh, it opens up potentially MORE roles for champions. As itemsets can now have highly specialised items the itemset becomes much more important for what role you fullfill. For example, you could make a support item that encourages your allies to attack faster because of your example-attacks. Tada, marksmen can now have proper supporting mechanics. However, said marksmen would do less damage than the marksmen using the ADC set.
It only has one real disadvantage: it reduces (percieved) choice. First off this is is largely a percieved issue as opposed to an actual issue. Technicly there would indeed be less options, at least until new items are added, as you've lost acces to a number of items. However, a large amount of the options lost would've never been used anyway. E.g. noone will build massive amounts of AP on Lee sin as there isn't any point to it, so denying him acces to rabadons deathcap won't really bother anyone... Secondly, the addition of new items with new mechanics can more than make up for any lost items.
Also, since people don't seem to get this. you DON'T lose acces to anything directly everything will be in an itemset that you CAN acces, at worst certain especially extreme examples will have lesser versions of said item. Udyr for example can still build a trinity. However if he chooses to build trinity he can't also build the high end defensive items. So you'd get the choice do I want to large amounts of damage, or do I want to be able tank large amounts of damage. As opposed to the current situation where he can do both effortlessly.
Why is the current situation bad
First of the difference between certain classes is minimal, and especially true tanks & supports have to make do with fairly awefull items as mentioned before. However, the biggest problem is the potential abuse of items that end up being extremely effective on certain champions. Now why is this a problem?
The first issue is that if every character has acces to every item in the game mechanics that could potentially be abused need to have increadibly low ratio's in order to prevent the abuse. As mentioned before take Leona, she has abysmall ratio's simply to stop her from going full mage, however as a consequence the bits and pieces of AP she gets left and right from items like frozen gauntlet are absolutly insignificant. If Leona wouldn't have acces to proper mage items to begin with these ratio's could be improved so the occasional AP would actually be usefull, or she could get acces to slightly altered forms of such items so she doesn't waste money on what is a very insignificant stat for her.
The second issue is that it allows for extreme effectiveness in some builds. For example a Udyr only needs a Trinity force to be one of hardest, and most consistent hitting, characters in the game, allowing him to make a full tank build, yet somehow still do increadible amounts of damage. Conversly, it occurs frequently that relativly squishy assasins build a single highly effective defensive item that gives a massive burst in survivability allowing them more than enough time to actually close up on opponents and then burst them down. Because these champions have acces to both high end defensive and offensive items they get to have the best of both worlds. Whereas characters that can only make use of one of the two types are left in the dust because that 10% extra defense isn't going to help if your opponent has more than doubled his damage output with one very effective item.
Especially this extreme effectiveness can be infuriating as more often than not, not only does it make for extremely effective builds allow the champion to function in multiple roles simultaniously, but it also results in a massive powerspike when said item is done. This often makes responding difficult if you yourself do not have something equally effecient to react with, and if you have nothing of the sort it feels borderline toxic as your opponent now effectivly wins due to massivly higher numbers as opposed to outplaying you.
How should it work
Now as people seem to fail to understand what I actually want. The point is NOT to simply take away say all high end defensive items from ADC and not give tanks acces to any offensive items. The idea is to do the following:
First all items get put into itemsets for each archetype, so APC, ADC, support, tank, bruisers, and so on. Certain items will occur in multiple itemsets, and certain items will have a different version in each set with (slightly) different stats. E.g. Frozen gauntlet might exist in all versions, but give less armor if it's not the tank-version, more AP if it's the APC version and AD if it's the ADC version.
Second, each champion has acces to each set, but once you start building in a set you're limited to that set only for the rest of the match, unless you sell your stuff, much like the gold items work now. Switching set midgame should be increadibly ineffective gold wise to prevent abuse of multiple sets.
Third, certain specific items on specific champions will be further adjusted to prevent abuse from the specific item, or to actually make it usefull. For example, we know AP tryndamere is toxic with high values of AP so we just reduce all the AP on the entire APC set for him, allowing the build to be potentially non-toxic as it can no longer reach immortality with his heals. An example of buffing a certain item to make it usefull is somewhat harder to come up with at the top of my head.
Fourth, a large amount of new items can now be made that are specific for each role in order to plug existing holes in the itemisation, for example the ADC set would need some defensive items that are usefull, but not as powerfull as proper tank items, whereas the tank set would need some offensive items.
Fifth, new items with new mechanics and interactions can now be made. For example, tank items that reduce crit chance, items like ardent censer that add new mechanics to existing skills, an actually decent version of atma's, a defensive glass canon item that increases your amor & mr by a small percentage of your AD, support aura stacking as a team, items that improve the effectiveness of CC, items that reduce the effectiveness of penetration, items that chance part of your damage into true damage. There's quite a lot that is currently not possible due to the fact that said items are pretty much guaranteed to be abused.
As you can see, you can still break the meta, quite easily even, you can still play every champion in every role. However, you can no longer make hybrid builds that use high end items from multiple roles to effectivly fullfill multiple roles with one champion and you can limit the powerspike certain extremely effective items would get. And you can now make a bigger distingtion between the different archetypes.
Examples of itemsets
As people still don't seem to understand how each set actually works and think that this would for example somehow stop bruisers from being bruisers because it stops hybrid builds I'l give a quick overview of some of the sets that should exist and what kind of stats/utility they'd give. The goal is for each set to fullfil a role & because other roles can't steal items from it they can get highly specialised items that would be extremely powerfull in other roles.
ADC/APC: Nearly completly offensivly focussed, very few options in terms of defense or overal utility. Most utility focusses on offense (e.g. sheen). Some mechanics that change offense into defense (e.g. an item that gives armor & Mr equal to a small % of AD, like <10%). Most defense relies on spellvamp/lifesteal and their ability to kill stuff. For these the best defense is the offense.
AP-Bruiser/AD-bruiser/Hybrid-bruiser: A mix of both defensive & offensive items, neither as strong as the carry or the tank set. Reasonable amount of utility. Imagine the items that are currently live, but with less stats on them and you sort of get the idea. E.g. carries get Hydra's with 75 AD, bruisers with 50, tanks get Randuins with 70 armor, bruisers with 45. Also a considerable amount of hybrid offense/defense items (e.g. hexdrinker). Mechanics that benefit from duelling as opposed to quick burst.
AP-Tank/AD-tank/hybrid-tank: Nearly completly defensivly focussed, in terms of offense you won't find much more than sunfire or thornmail or something (this would be improved over life by the way as these are currently lackluster, but you get the point). Considerable amount of utility but mostly defensive focussed (e.g. added slows, or personal shields). Mechanics that benefit from long drawn out fight. Some mechanics that change defense into offense (e.g. Rammus' passive)
Mage-support/Fighter-support/tank-support: Lots of utility, lesser INDIVIDUAL stats than their non-support counterparts. Mechanics that focus mostly on helping their allies. Mechanics that they themself benefit from having allies around and thus rewarding them for supporting, e.g. locket doesn't only give all surrounding allies 20mr, but the support gets 5mr for each friendly champion near them. Several variations due to the difference in support styles between say Janna & Braum.
These are some rought examples for most roles, we might need more sets (e.g. maybe an assasin set) and maybe AP/AD sets could be combined I've seperated them for simplicity. Hopefully this clears up some of the trouble people had with understanding how itemization would actually work if you're limited to one set.
So, now hopefully that is all clear now and people stop thinking I want everyone to only have acces to one item and adhere perfectly to a strict meta with no choice whatsoever as opposed to what I actually want which is better items for certain roles/champions and a limitation of the super effective items on certain others. Feel free to comment and discuss and such.
Anwsers to certain questions
As questions are asked I'l also put the anwser here so I don't have to anwser everything ten times should this ever draw much traffic.
Q: Why not just buff ratio's like leona's so the bits and pieces of AP actually become usefull? Or nerf some of the aspects of champions with super effective items?
A: The issue with buffing stuff Leona's ratios is that she'l be used in sololane/jungle as an mage or AP bruiser (similar to how AP cho, or nautilus work) because a higher ratio with proper AP levels would be broken. However with her current AP you are in this awkward spot where the bits and pieces of AP you get from stuff like frozen gauntlet are just meaningless. The issue here is that such low ratio's don't do anything if you only get a handfull of stats. Whereas when you have proper ratio's people will try to take their advantage and abuse it with in this case a proper mage build. So if you'd improve Leona's AP ratio's not only would the AP of gauntlet suddenly be usefull, but the AP on Zhonya's would be even more usefull. I find it highly unlikely a balance will be found to prevent this kind of abuse while keeping the lower-value AP items usefull with just number tweaking. It's the reason why in pve games generally gear is limited to certain classes, so they can give the mage the high magic values while the paladin gets high enough ratios to make use of his more limited magic values.
Similarly, nerfing the champions that have these kind of super effective items would generally require you to break the champion. In the case of Udyr, unless his base AD becomes nonexistant Trinity will always be a massive powerspike to him. Or any sheen item on him for that matter. In this case it's the mechanic of the item that becomes broken as opposed to the actual values. Liandry's for example suffers from a same issue, on the right champions it can be abused to make for hilarious damage outputs (try it in combination with Rylais on Nasus and Mr penetration runes, his ulti will now just flat out kill champions that don't build much MR). Similarly on brand liandry's adds 8% current health damage to all of his damage with just the passive, you can nerf brand all you want, the item will still be a must have offensivewise.
For clarity: I mean, regardless of the actual values sheen'l be good on Udyr because it synergizes well. Now you can potentially nerf parts about sheen or him to balance that out. However, if you nerf Udyr, you'd end up making sheen mandatory if he wants to do any damage, and if you'd nerf sheen you'd end up making sheen useless for other champions who have a less absurd synergy with it(and ultimatly for him too). And if you nerf either too much they'd simply be left behind for other more dominant picks. Hence just tweaking values won't solve the problem, not without creating new ones that are at least as bad.
The only real possibilities here are to nerf or buff an item. However if you give gauntlet the AP necesairy to make it feel impactfull on Leona it'd take like 80 AP which would make it well, an extremely good mage item and squishier mages would start taking it to increase their defense without losing much. Similarly if you nerf trinity's proc to more acceptable levels the item would fall out of favor because champions who don't get the same large powerspike from it will just go somewhere else. In the case of trinity, it was relativly recently buffed to set it apart from gauntlet as an offensive item (from 150 to 200% base AD if I remember correctly) because apparently the fact that gauntlet came with freaking armor while Trinity had AD, crit & AS wasn't enough to set it apart as the offensive choice. Which frankly is idiotic.. but it was true that gauntlet for a while was much more popular, even on squishies, and because riot wanted squishies to use trinity as opposed to gauntlet they buffed it to a point where the passive singlehandedly is already one of the best offensive items on anything that has the CD's for it... And thus all the udyr's stopped using Gauntlet because the defense and added slow was not worth the massive difference in damage...
Fine tuning the stats and ratio's doesn't do much more than just have the biggest powerspike sway between one or two extremely effective items for these kind of champion & item combinations. And lowering it enough to no longer have it be that extremely powerfull will likely mean that the item/champion becomes useless in most situations or others will just be massivly better now.
Q: Why do support items need to be usefull on their own and not have any major drawbacks for the supports, like the gold items have now?
A: As for the exclusive support items, obviously items that help your allies should come with a drawback in the case you're not using it to support your allies. If only because that supporting power of the item is now gone. However, take for example bulwark. The problem with it was that everyone and their mother started using it as the goto MR item because it had good stats even on your own. We then for a while had a locket that only gave 20mr and 20 armor, which as a support felt horribly weak because it didn't work as your MR or armor item. The only reason to get it was because it helped your allies, not because it was actually a good item. Now it's back at 40MR and supports actually are using it again because it now functions as their MR item. But bruisers also still use it frequently. Similarly take zeke's herald. Does anyone actually use that thing? The aura is decent, however the actual stats it gives to the carrier are bad on pretty much everything. The issue is that as a support, the items that I build need to actually be usefull to myself too. My main focus might be helping others, but if my own stats are low and my abilities are weak my help isn't going to amount to much. Furhtermore, it's kind of lame if you're giving everyone loads of stats but your own abilities don't actually do anything.
Q: Isn't the problem extremely good steriods on certain champions as opposed to acces to very effective items?
A: Yes and no. It is indeed part of the problem but take for example Yasuo. His shield is quite powerfull. However, adding in a randuins omen suddenly almost doubles the effective health that shield provides pushing it from powerfull to borderline broken. But, if you'd lower his shield it'd be useless without the large chunk of armor Randuin's omen provides. Tanks often suffer the inverse issue. Braum for example with a full tanking build is nigh on unkillable, if he however isn't done yet with his build, or takes any offensive item, he suddenly loses a significant chunck of his powers. If I didn't know better I'd almost say that certain champions have been balanced under the assumption that they ABSOLUTLY would not use certain items, or ALWAYS have certain items. Which just seems silly if that were true. Anyway, the point is that simply tweaking their values, even extensive tweaks, aren't likely to do much. It's usually a mechanic that is extremely powerfull, so reducing the numbers will nearly always mean the mechanic is now useless without said super item.
Q: Won't supports become much more powerfull?
A: Yes. However, the reason they currently are weak is because they only have acces to awefull items. As a consequence they are in a odd position where they are balanced to be relevant while assuming they will only build awefull items. Giving them good items would obviously make them more powerfull, and as a consequence certain parts might need to be nerfed to stop them from being overpowered, however on the whole I think it would be better balanced than the current situation where an entire class of champions is balanced around the notion that the items they will get are borderline useless.
Q: Won't supports start dealing too much damage if you give say leona a Frozen gauntlet with 80AP or something?
A: No they won't. First of, the AP they get currently is so low that with their ratio's they might as well get nothing (frozen gauntlet adds less than 3dps with its AP to Leona's rotation... having a minion follow her around would do more than that...) Secondly, the supports that aren't mage supports do utterly neglectible damage at the moment as soon as they are up against an opponent with any defense. Try fighting say Udyr with Leona, Udyr's healthbar will barely move. At the moment it is so bad that if said support can't immeadiatly burst down their opponent they will most likely not win the fight, regardless of how low the opponent is and how healthy they still are. Simply put, it is idiotic that say a Udyr with 10% health remaining has nothing to fear from a Leona at full health late game. Giving them a meaningfull increase here would mean that at the very least supports can now actually win fights where they have a significant advantage (e.g. a tower backing them up, enemy at low health etc.)
Q: Won't this limit options in terms of metabreaking?
A: No it won't go read the freaking text again. Everyone can still acces items from each set, just not at the same sodding time. You can still play support Ashe and carry Sona or whatever tickles your fancy. In fact certain combinations might become more viable as this would for example allow for supporting items for marksmen. The only options that would be made impossible are options that are absolute poison. For example AP tryndamere. Apart from that it will only make a greater distinction between the different roles. In case this anwser still isn't clear: NO IT WON'T!
As for certain builds no longer being viable like throwing a blood thirster and a deathcap together, yes those no longer would be possible, but I deem irrelevant as they are just idiotic builds that really shouldn't be attempted in the first place. And before anyone starts with the mantra of freedom and being allowed to make mistakes again, I don't consider blocking that kind of sillyness taking someone by the hand. And it'd stop the extremely effective builds that currently exist from being possible 'which is well the whole point.
Q: Won't it be confusing to have many more items, or the same item but with different stats?
A: I presume people have some intelligence, though then again people are morrons. But that's more their problem than a fault with the system I propose. As long as the distinction between each variation is made clear it should be understandble. For example, colour code each variation of the same item. So the carry version is red, the rank version is blue and the bruiser version is yellow. Should be easy enoug to make it clear at a glance which set someone is building from.