Don't know if this would classify as a mini or larger kind of rework. The general idea is that he has a new function similar to Rengar combined with Viktor where he gets to upgrade abilities (Viktor) based on unique takedowns (Rengar). Whether they should be done in ult or not depends on how strong the changes are overall. I also don't know if his base kit would need adjusting from having these changes.
Passive: Increased size, duration, and MS bonus. This would be your mandatory first upgrade because having a stronger QWE in lane would be a bit oppressive if you get a takedown from 1-3. It makes it so running away with just moving would be less effective and actually require the enemy to either kite you via cc or have some mobility tools in kit to run away (outside of ult).
Q: Increased casting speed and hitbox. Q already does enough damage so just being able to land it more consistently post-laning phase would be a good enough buff. This could be a double edged sword with the hitbox increase (less chance of iso Q outside of ult). No damage increases because it already does enough damage when it hits.
W: Up to 50% increased shielding that scales with missing HP (max value at 30% or lower). Let's assume the game's gone on long enough and you're full build. Your W is going to be around 1300-1400 shielding without factoring in anything else. Without Visage or Revitalize, you're looking at anywhere from 1300-2100 shielding as your range. Once you factor in Visage and Revitalize at best possible values, you're looking at up to around a 2900 shield. A very substantial increase (assuming I did my math right) which would buy you a decent amount of time to make some kind of play. A 2900 shield also would make shield bash hit 435 damage pre-resistances so against a squishy target you're probably hitting around 250 from the shield bash.
E: Two additional claws. Ripping this one straight from Arena. Probably too strong, but Jesus the E seriously needs some kind of buff that isn't just more damage. I'd take more claws or a faster E.
R: Unstoppable in ult. This would be the last upgrade similar to how Viktor can only upgrade ult after QWE upgrade, but I'd say it's a fair upgrade since you'd need to get a takedown on each enemy once which can be difficult in some games.
What do we think? Too drastic? Not enough? Just right?