New Feat, feedback wanted

[Grim Reader]

I'm adding a new feat to the game world I am building. Is it overpowered or abusable in any way you can see?

Adaptable Mastery (Half-Elf). Prerequisite: Multiclass Mastery.

You may mix and match favored class bonuses. When gaining a level, instead of picking a favored class bonus as normal, you may pick the favored class bonus of any class you already have levels in. Any level-based variables are based of your character level. If you have the ability to pick multiple favored class bonuses, you may do this once for each, but you may not pick the same one multiple times, even if it appears on more than one list you qualify for.

[rferries]

If you're investing a whole feat I think it's fine; I don't actually play Pathfinder but I think the favoured class bonuses are usually very mild benefits anyways?

[nikkoli]

PF favored classes can range, since it's for half elf they would have the half elf, human, and elf pools to draw from and it varies by class how strong they are, like human for sorcerer is +1 spell known of any level but your highest.

I don't think this would break anything, most favored class bonuses are keyed off of abilities that class has so multiclassing a lot takes away from how useful they are for the 1/3-6 level ones, or for extra use ones when. You aren't advancing the dc of an ability with that classes levels.
I would let the feat go into my games as is.