Good question. It's a niche game that aims to do something specific rather than trying to satisfy everyone's tastes. I've mentioned a few times that a female MC will be added to the Master Mode soon. I think it makes a lot of sense to have a mistress as the main character. However, there's no point in having a female sub MC at the moment.
Sales are an important factor because there's no point in developing a game that requires so much time if it doesn't generate income. That being said, I'm trying to create a decent game that does specific things very good, rather than making a game that probably won't ever get finished.