Assassin balance idea already in game

I just watched the new Tristana champion spotlight and it got me thinking; why don't we balance assassins like Zed in a similar way? What I'm talking about is ability resets on kill or assist, for assassins perhaps changing it to be just a kill reset but that's up for debate. The idea behind assassins is meant to be 'high risk, high reward' so why not reward assassins with an escape upon properly doing their job. Zed could be allowed to teleport out once he kills the target, fizz could get a troll pole reset, Akali- well late game Akali is kinda silly how she can still be hard to kill but assassinate tanks at the same time but that's a different problem.

Anyways, this would mean balancing more damage into an assassin's full combo so they can go big or go home instead of not needing their mobility for damage and using it to escape. It'd be like Tristana's rocket jump reset; you can go in but you better be sure you get the kill otherwise you have no escape. Anyways, what do you guys think? Thoughts, comments, ideas? I'm not trying to hate on assassins but they are a bit too safe (Zed specifically) if you ask me.