Okay so first off this is just what I hope the Upcoming Rework is like.

The Rework

Passive - Sion builds up Rage with every Auto attack(out of 100 rage) and rage decreases after set amount of time out of combat. Sion gains 0.25% life steal for every 1 rage point.(that's 25% at 100 rage)
I like this idea because it give him the ability to be very hard to kill if you let him get a footing in lane, but also makes him weak to bully lanes.
Q - I think this definitely needs to be a short dash move that slows targets struck at the edge of the dash. should go through units so he can ignore targets he doesn't want to fight, but make it really precise so only the target at the edge of the dash is effected at all. He should retain the weakness of have little to no escape, to help this the cooldown on this move should be like 20 seconds and cost a % of your current rage but  CD goes down by 50% if it strikes an Champion and the Rage is refunded.
A move that functions in this manner makes him relate more to his new lore. Punishing you for trying to back out of a fight, but rewording you for staying until the end.
W -  An empowered strike. Sion readies himself for a devastating swing that arches in front of him, dealing good AoE dmg, so this move is on like a 2 or 3 second charge and increases his MR and armor while charging by a small amount. The more damage he takes while charging the more Bonus dmg this strike does (with a cap on Bonus DMG).
I think a move like this would be a cool high risk high reward attack, while you charge for the move you stop putting out dmg and are rendered more vulnerable, but your opponent must be sure that they can dodge your attack after taking advantage of your weakened state or kill you before this devastating hit occurs.
E - I don't think the idea of this move needs to change, but it should be improved on. The HP cost per attack should be 5-10% of the dmg you deal or around that number or decreased Healing effects while toggled on. In turn it should be a reflection of this increased risk by changing the flat Bonus AD to a % increase that maybe goes as high as 50%  at rank 5.
I just like stats that remain about the same effectiveness at far as punishment and reward go through all stages of the game.
R - Multiply the Life steal received by the passive by /2 /3 /4 (also multiply the rage gained each Auto ) as well as give him /.10% /.25% /.5% attack speed for each point of Rage this keeps the Ult the same, but gives it a weakness as well. Also increase the size of the AoE the team healing effect, well affects.
Again this move gives chance for counter play by giving it the weakness that if he doesn't have rage built up it doesn't help him much. However having the potential to heal 100% of the dmg you inflict is crazy

This is what I HOPE the rework is similar too hate my idea or love it this makes a lot of sense to me. The whole idea creates a champion that could carry, but also has a lot of room for counterplay.