What I think ekko should be.

So here are some mechanics i think he could use:

Rewind mechanic:

You partially reset his cooldowns on every 3 hit passive proc. This allows him to go in, and get back out safely. In compensation, you nerf his dmg.

Baseball skillshot mechanic:

Let him target his timewinder with his e...this is kind of cool. If he could e to the timewinder, he could sort of hit it like a baseball in a direction of his choosing. This would be really neat and would help him proc his passive 3 times on one target from range. MIght work like this, q then e then if you hit q without using the blink, the timewinder will return to you and you will hit it in a direction based on your mouse position. Compensation, Its a very difficult skillshot because it ricochets. Its not going to go in exactly your cursor direction. It goes in a direction that depends on the direction it comes back at you and you sort of deflect it with the cursor position. Sort of the way light bounces off a mirror. Your cursor would indicate the normal vector from the surface of the mirror. If you aim your cursor directly at the timewinder, then it goes straight out. If you aim your cursor in a 90 degree angle from the angle of approach, then you bat it behind you. Works like a mirror or like a ball bouncing off a surface.

I think if you also let him blink to the timewinder instead of reactivating his q then hes a cool as fuck champion that you wouldnt ever build tank. I think in return for this, you could decrease his base dmgs by a lot and would really really need to. But since he is sort of stacking all of these abilities on top of one another, his dmg in lane would still be pretty good. He would be really reliant on difficult skill shots and could be allowed to scale really well. Idk. I just think that the baseball thing would be an awesome way to afford him less early dmg, but maintain his laning presence until he builds some AP.