Just as the title says, I think they should make Phials of Fantasia as a purchasable item at the Tome Shops in Mor Dhona, preferably Philosophy.
Race really doesn't play that much importance in this game and the only thing gender determines is what item you get during special events, so changing them would pretty much be cosmetic. It would kind of be on par with buying Keeper's Hymn from the Grand Companies.
I also don't think it would intrude on the Aesthetician because he would still be a more affordable option for those who like their current character or aren't that far in the story but just want to change minor details like hair or face paint.