I say this as someone who likes the cop LI a LOT. Less is more with Love Interests. Better to have deeper, richer content that makes a bigger deal with plot and character development, than a massive shallow pool that gives everyone a single taste and nothing more.I don't know how you define main, but probably the girls at the house + Lilith. Rest is not completely decided yet, I'll probably do a new poll on the popularity of the girls after next two episodes to get a better feel on things.
Make one girl afraid to do anal, and slowly work through that together. Or maybe the mom just can't get on board with the idea of a threesome with her daughter.... until you convince her. Putting the harem together shouldn't be simple or easy like collecting fucking baseball cards*, it should be the heart of the story, or at least part of it.
*TS fell into the trap of just throwing girls at us without any chase, and having them all just accept being in a harem. Which cheapened the achievement IMO. I say this with great love and respect for your first entry Dev.