Zilean; New Passive Concept
Zilean's experience aura is the worst feeling passive ever for the Zilean player (I actually play Zilean, so I should know about that at least) besides it has zero late game benefits since you cannot go beyond level 18 obviously.
Another thing I would like to see if some kind of proactive attribute to his ultimate rather than his ultimate being only reactive, I do not know what exactly can be added for this however.
Time Stone (Passive): Ranks: @levels 1/5/9/13/17 Zilean creates a time stone directly in front of him if he stands still for up to 12/10/8/6/4 seconds, up to a maximum of 3 time stones at a time. Time stones grant vision around them, last for up to 180 seconds, and cannot be destroyed unless Zilean exceeds the time stone limit.
Additionally, if a Time Bomb lands on a Time Stone then the Time Bomb will instantly detonate and apply its stun duration, the same enemy can only be stunned once every 6 seconds if they are stunned from a Time Stone.
Zilean grants 8% bonus experience for himself and nearby ally champions around him and his Time Stones (bonus experience cannot overlap).
[Cannot be destroyed, but can still be disabled by enemy red trinkets which includes their vision they grant.]
Chronoshift (R): If the chronoshift bomb does not resurrect its target then it will explode to stun struck enemies for 2.25/2.75/3.25 seconds [500 units radius].
This is a spit ball idea for a pro-active ultimate; the thought process is treating Zilean's ulted target to be like a bomb about to go off, you either diffuse it or it explodes to cause massive devastation to your team for those caught in the blast radius. But again this is a spit ball idea and there are many many different things that be here and possibly better suited too.