There are some benefits (namely the appeal to players that have various sexualities that don't only enjoy male/female content but can even customize their gameplay to their own fantasies, you could even draw in gay males, futa fetishists. and even pure lesbians (by adding female mc option. Never mind adding a potential party system enabling group scenes for or voyeur scenes for those that enjoy such content. The trade off is ultimately appealing to a larger sexual demographic thus needing to meet more demands for content over smaller audience and subsequently easier content demands.
Side note regarding futa: There is a very firm split between futa enjoyers for futa with or without balls (you'd need art for both versions to not lose one or the other.) (Yes this is a thing) I should know I'm all for futa with balls and have seen plenty of balless futa enjoyers and fellow futa with balls enjoyers argue over the matter. So just be aware of that potential argument when adding the futa art to make that toggle accordingly.
( mind you I personally would like addition of futa and male enemies I do understand not everyone would.)
A couple implementations Ideas for this:
1 Global Toggle, Make it so eventually every enemy has 4 models: female, futa (both versions) and male. then the player can enable/disable to suit their own preferences.
2 Side quest with global consequences, (make a cure that fails and changes the enemies to another flag, the player should be made aware ahead of time about outcome before accepting quest. (different outcomes from said quest ( success=alternate ending) different failures such as futa enemies, and/or male enemies.
3 Recruited Allies such as Malo, or others with the roommate system could be given TFs by player to change them (and become party members too) also post battle scenes with either the mc and party member(s) having sex with enemy, or having the party member do the fucking (or just watching) party members would interact with the exhibition stat. (additionally this system could be used for other kinks and more fleshed out side characters.)
4 Npc "art packs" change all art to another type (don't recommend has its both convoluted in execution and makes all npcs only one gender. (also would need dialog swap for male versions)
5 content opt in thus global enable via the park brothel building, maybe via the gloryhole where a futa requests you to service her starting or ending all futa content. Same for male content.