Oof, never a good idea to leave story and fetish content up to anyone else. You should know the audience you want to court and then make the game that suits that group and still upholds your vision. Games and other stories made by committee almost never end up well. I have no doubt there are a bunch of thing you have ruled out 100%, like will you leave the inclusion of necrophilia up to supporters? NTR ought to be treated the same. Unless it is what you want, in which case please just say so now.
Harem and NTR don't mix, you say you want a harem story. So, I'd recommend you make that game since you have clearly said it will be in the game. No need to mix two fetishes that are polar opposite and drive away the players that want the genre you have already planned to include.
Just a bit of food for thought: While NTR is often considered by westerns to only be a current love interest cheating on the Mc it should be noted that in Japan and for most people who dislike it, NTR includes NTR adjacent content as well as all the "Not technically NTR," content that some try to slip in such as flashback or "Not love interests yet," where girls bang other guys. None of that type of stuff adds to a game that isn't an NTR focused game. Some even consider lesbian stuff if the player (not just the Mc but the player as well) gives full consent.