The scenes in this game are not rendered real time. Having two different versions of a character would require every scene to be pre-rendered all over again, in addition to the code to check which version of every scene should be shown to the player.
Harem Hotel is a game made in the same engine, and that game is now nearly 13 gigs in size, and much of that stemming from the fact that main characters have a bunch of outfits (and in one case, adjustable breasts), so every repeatable animated scene has like 5-10 different variations, every one of which is pre-rendered video.
Oh right, and as far as your other post goes. Seems silly to curse and kink-shame on a forum for an H-game just because some people have different preferences to you. Are the boobs a bit much in some of these games? Yeah, but in the end the artists make their choices, all we can do is choose to play their games or not.