This is about vision in League of Legends, and the ways Riot can communicate information to the player. To a larger extent, this should apply to RTS mechanics as a whole, as the isometric perspective is a common feature and happens to be the best way of gaining visual information (as opposed to a over-the-shoulder or 1st person perspective).
I was playing Baldur's Gate 2, the old school D&D game, and I noticed that it features several spells and abilities that play with vision in slightly different ways. In fact, the entire 'School' of Divination magic in D&D is about sight, stealth, detection, and denial. Riot could draw some inspiration from them - I know I have. Something else I noticed was that D&D also feature several spells whose sole purpose is to undo the effects of, or cancel, other spells a.k.a. counter-spells. The word 'counter' gets thrown around a lot in League, but no where does it hold onto its original meaning quite like it does with the relationship between true-sight and stealth.
With Riot so big on 'counterplay', why is there so little for stealth and even less for true sight? On top of not having a lot of options for dealing with stealth, the main things that counter stealth (by offering true sight) do so in the hardest way possible. There are no activation delays, no telegraphing, no neat interactions, just flat out 'now you see them' (at instant speed!) - provided you spent 100-250 gold to arm yourself and had the mental wherewithal to use it. To add insult to injury, the champions with stealth have no ability quirks effecting true sight - even when it would behoove them and be flavorful.
It got me thinking, why is League so limited with its vision effects?
With so many different items granting combinations of useful stats and cool effects in a unique functionality, I feel it is a shame that vision is allowed to linger behind when the design space is largely unexplored. Don't misunderstand me, Riot's introducing the trinket system in S4 was a great first step. Another great step that may have gone unnoticed, was adding smite buffs to the jungle monsters, namely the Wolf Spirit from the Wolves and the Razor Sharp buff from the Raptors. Riot is, slowly but surely, adding more (and varied ways) of playing with sight.
The most significant step, however, was 
Rek'Sai with her 
Burrow and its Tremor Sense. Such an ability is unprecedented in the League, as it's the 1st 'detection' ability, as far as I'm aware. I'm defining 'detection' as 'providing imperfect information without providing sight' (i.e. targetability (in most cases)) and itself not being affected by vision denial such as Template:Cctip.
Likewise, 
Nocturne and 
Graves and 
Tahm Kench are the only champions who currently can deny vision with their abilities. More effects like this need to happen. Why? Because having another form of Sight Denial takes the pressure off of Stealth. It is no longer the only 'sight-based trickery' that player's must contend with. My wish is that Template:Cctip, rather than it's current form, function in a similar manner.
So some distinctions need to be made. Sight, is self explanatory, allied units and wards give it, as it dispels the Fog of War, is blocked by terrain and brush; Concealment, is what terrain, the Fog of War, and brush offers, effectively making you untargetable; Stealth, which is a relative of Concealment, offers untargetability regardless of other forms of Concealment; True Sight, specifically interacts with Stealth (ideally in the form of soft-counters), revealing stealthed units; Detection, which is distinctly different from Sight and True Sight, does not provide targetability and grants only imperfect information; Sight Denial, which Concealment and Stealth fall under, also includes 'pseudo-stealth' effects such as the new Template:Cctip, and the aforementioned trio's skills.
The goal here (what I would like to see from Riot) is to give players options when it comes to gaining information. Just like you build for the situation, and spec your champion your way, and pick champs based on the matchup, having variable options where none is strictly better than any other but situationally more appropriate would be great for the overall health for the game.
Most of this is speculation though. And as much as I'd like to see something along these lines, I'd probably have to make my own game to implement them. I can dream though.
2nd Inventory (The)
The most important change: the trinket item key (the 4 key by default) would become a button that toggles between two six-slot inventories. The one contains regular items, and the other holds only wards, consumables, and trinkets. This will enable champions to participate in the vision game while not cluttering valuable inventory space. Champions can only carry two wards with them and only have two down at any given time. Though this limit can be increased with masteries and specific item purchases. Champions are also limited to one trinket at any given time.
Blinds & Denials
Template:Cctip no longer causes 100% chance to miss, instead it now reduces the targets Template:Cctip range and removes shared champion Template:Cctip, including towers and wards, similar to that of Graves' 
Smoke Screen, Nocturne's 
Paranoia. These changes give some champions a form of vision-denial that can act as a 'pseudo-stealth', i.e. it provides the untargetability that stealth offers but in a different functionality. We also need to see more of these effects, ideally with each having its own quirks and conditionals.
Detection
Vision has been largely binary, up until Riot introduced Rek'Sai and her Burrow complete with its Tremor Sense, as I explained above. I would like to see other forms of this, as it counters stealth in a way that doesn't strictly undo stealth's primary effect (untargetability). Some examples include 
Rengar's 
Thrill of the Hunt's Infra-Vision (notably being a special case of detection providing targetability), the once planned Mandrake Ward (reborn as the Snitch), a possible Aura Awareness that grants 'sight' of enemy champs via a bluish visual FX within a certain range, but no specific info about which champs they might be, X-Ray Vision that grants 'sight' beyond terrain and through brush via a grayish visual FX, and a warning indicator such as that with Elixir of Perception's Intuition.
Stealth
All invisible champions can be seen within 75 (maybe 100?) units edge to edge (i.e. well within melee attack range) unless otherwise stated. Typically, a successful attack or spell will end the stealth early, thought it varies by champion. This would be a small nerf to stealth, its I like to think of it as more a a homage to Eve, as she was the 1st champion to have something of this type implemented. This built in form of counterplay is another weakness, obviously, but it demands greater positioning (skill) from the player using stealth, highlighting exceptional players. If a Vayne tumbles onto you, or Shaco misplays, they die. Also, Teemo can't just sit in a bush with you right on top of him. He's camouflaged, not some sort of hyper-dimensional being occupying the same space as you at the same time...
Terrain (Champion Created)
Champion created walls, such as 
Anivia's 
Crystallize, 
Karthus' 
Wall of Pain, and 
Trundle's 
Pillar of Ice, now interact with vision, blocking it as regular terrain would (as with Anivia & Trundle) or inhibiting it to some degree (as with Karthus). This is another way to play with vision that also serves as QoL buffs to some champions. Think of the flavor!