How about changing Rengar Empowered W. To a cleanse which grants an ability shield (Noc W)

Instead of the gutting changes

Players are right if you remove his cc immunity in a way where he can only cleanse he ll be in a really bad spot

This is how empovered W (My version) would look like

Rengar cleanses all CC still gaining health the same way he does, still gaining movement speed, But he also gains a shield which blocks next ability (Basicly nocturne W). Duration of shield 2 seconds

It would be Worse then Gaining olaf Ulti but he would still be able to function

Pbe changes for rengar ll gut him