Tristana vs. Kha'Zix
No one can deny that Tristana and Kha'Zix have similar jumps. Besides when and how they reset, the major differences are that Kha'Zix's jump is much more instantaneous while Tristana's provides a heavy slow.
Now if you take a look at Tristana, her roles are Marksman/Assassin. But to be honest, her jump delay is a huge problem for any assassin type gameplay. Why not make it so that her jump is quicker when she tries to assassinate someone?
All you'd have to do is make it so that if Tristana jumps a subsequent time (say 5ish seconds) after she has previously jumped, it will be an instant jump like Kha'Zix's. That way it would encourage people to actually be able to play her more assassin-like (which I very much enjoy doing) while not making it defensively overpowered, or even very strong in the Marksman role.