Why can't you just bring back AP Fizz but remove his Untargetable skill?
Fizz should return back to his AP self as a mid laner like months ago, BUT remove his untargetable ability from his E. There should be no reason for this champion to have a free Zhonya mixed with an escape/utility to slow enemies. All that in such an early level with a late game low cool down.
Fizz isn't a fair champion at all, he is too slippery and there isn't any counter play that you can do when he uses his E. It's more worse than Yasuo's wind wall because at least when it comes to yasuo's wind wall you can still get him from a ground skill like Chogath's Q while Fizz's E is immune to EVERYTHING.