Hey, hey, hey, don't take it as if I were discouraging you, remember the first rule: If it turns you on, GO FOR IT! I mean, I actually have one scene with a trans men (FtM) in my game, for fucks sake. Of course, that scene brought the dreaded futa/trans tag, and I had lots of people asking about futas and trans girls in my game... just because one scene with a trans man, and I specified it on the dev notes already.About the femboy content. Well if that's what it id then I'll just hint a bit of it from the initial game and cut it out for a bonus story if enough people liked it.
Something similar may happen to you if you include a sex scene with the femboy and the gay tag, and that tag can be annoying if you don't have a gay focused game. But don't start cutting content just because you're afraid... it's enough to deal with patreon and their hunt for incest/rape/bestiality/loli and you're going to cut more content? don't do it. If you like it, include it. Just be wary of the tags.
Unless it's a tag that you want to... I dunno, attract gay players? female? or because the story demands it, in that case it's better to cut it off from the game. I included one scene with a specific kink (sissification) on my game because the plot lead to it but, holy shit, my writing on that scene was awful, it's not a kink of mine. Do not fall on that trap.