Would be nice if one of shacos basic ability's had scaling cooldowns.

So what are you nerfing to compensate?

Scaling cooldowns are usually either an incentive to max an ability first or a way to limit the up-time of an ability in early game if it's definitely not the one you want to max first.

Fiora is a good example of the second case: Riposte has a very high cooldown in early ranks so that she is somewhat vulnerable in laning phase but it decreases with ranks so that she can function in team-fight in late game. Illaoi is a good example of the first case. Tentacle Smash scaling CD versus Harsh Lesson static 4s means that you tend to max the Q first.

So, why would you want scaling cooldowns on Shaco? Remember, changes just for the sake of change aren't a good idea. A change must have a purpose.