We have plans for some characters to change costumes if some specific things are achieved. For example, at a later date we plan on Luke changing costume for players who reach a specific point in his story — beyond changing his pants and shirt, he'll put on a very stylish and personally meaningful jacket.
But it's not going to be like what players can do for Asterion, no. With Asterion you really can pick what he wears, but with the rest of the staff the clothes they wear is tied to what happens in your playthrough.