This is just a suggestion, but I was wondering if Zhonya could be a toggle (where you can cancel the ability duriation early). A lot of the time it's used as a way to 'stall' for more time (lulz) until your teammates can clean them up. Half of the time when you do activate it, players know exactly when it'll be over and could propertly punish (even if you do have an escape spells like Flash). By giving it a toggle, you open up more possible things to do with it such as
* Smoother escapes
* dodging abilities/ults by merely clicking the item again to end the item early (thus beind able to still keep pace with your team if
* Proper counter attacks (meaning it can be used for offensive stratages)
By ending the ability early, you still have to eat the 90 second cooldown, but it'd be so worth it if you manage to make it work.
EDIT: alright, based on what you guys say, it would be a bit too op. I can respect that, as it was merely a thought. ^^