That's a very good question. I think having a harem is a big thing for a lot of players. Which makes developing rather complicated because of all the possible harem configurations and branches.
True, it really is more work to have to develop characters, stories, personalities, how you will conquer and how the story will follow, I wish you luck and success for that. But then you already know the 3 topics most desired by your audience: harem, incest and pregnancy, why don't you ask if the audience would like some more? If there are more than 1 you choose at least 2 to add to these topics.