What if Aatrox's ult turned incoming CC into DoTs
This way he would be able to realise his fantasy of lifestealing sword monster, while giving more counterplay than simply being immune to disable. This would create a pattern where Aatrox and his enemies race in lifesteal and damage rather than just disabling and bursting him.
Every damaging CC would still fully apply its damage.
EDIT: indicative conversion. Note that all of this stuff stacks. Also he's considered as affected by CC for cases like Ashe's crits, and can't break channeled CC by leaving range (ex Malz tether doesnt break and stretches further than max range as Aatrox moves)
Conversion time window: 1/4/7 secs from ult cast
Slows: 1/4 of slow% as flat for the duration ex. 60% slow -> 15 damage/sec for duration of slow NOTE: since he doesn't actually get slowed, affecting him with other slows will stack and not just consider the highest one
AS slows: like slows.
Silences: 40 per sec for duration.
Blinds: Aatrox's autoattacks deal no damage but proc lifesteal and Blood Thirst
Roots: 60 per sec for duration (ouch morg) Stuns: 70 per sec Suppresses: 100 per sec
Knockups: 100 per sec
Knockbacks & grabs: 1 damage per 1 unit of max possible displacement, distributed over 4 secs.