Something I've always enjoyed is Tentacle hentai. Tentacle Rape is really big in Aisia, and I feel like a Tentacle Boss would be interesting to face. It could whip the player's character, or as a secondary minigame force it's way under the player's clothing (if any is on.) and begin pulling outward, forceing the player to break free. Also it could restrain a player while computer enemies attack. I also feel like there aren't enough Female characters. I've only come across one 100% female, the rest are either herm or male. I think the game would work well with more female characters and pull more of an audience with those who prefer M/F and F/F (if you decided to have a female playable character.)