What would be the most sought after topic by your audience besides incest and pregnancy?
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.