I literally just got an idea that I thought was quite clever and original. I could be wrong, but either way, I must share.
Stories where humans or angels are captured or visited or corrupted by sadistic and sexual demons, those, I find, are quite common. I'd be interested in doing the opposite. Specifically, a game wherein a demon - a succubus or sorts - is captured by an angel or some other godlike being, and given absolutely no outlet for her desires. I would definitely like for her to be extremely lustful, and extremely explicit in what she says and what she does.
That being said, I think it would be a terribly unsatisfying story if nothing happened beyond the demon being restrained and deprived of the sensations she craves. I'm also not too keen on playing an utterly austere and puritanical angel. It would require some effort to make it interesting and not just another 'forbidden romance', but I do think it could be interesting for some sort of twisted affection to develop between the two, who are initially mortal enemies.
If this sounds interesting, do let me know - preferably in a PM!