This topic was raised once before early in the game, but I don't think anything came out of it other than a Dev saying it was an interesting idea (I'm not completely sure if this may have already been implemented since I haven't purchased any playable alien races yet):
The playable alien races in the C-Store should unlock their parts in the alien generator/character tailor when purchased.
I know I'm not very interested in playing with any of the C-Store races as my captains, but I wouldn't mind being able to customize alien BO's or even captains with some of their parts. Being able to do this would definitely make me more likely to purchase these playable alien types.
The only change I would make to them is probably give federation klingons a discount since their parts are already in the character tailor.