is it going to be avoidable?
Good... now another "insight" to help you develop the game... girl on girl should always avoidable aka not happening if the player decides so. And never behind MCs back either, or you have NTR again. Most people aren't as forgiving as they used to be when it comes to lesbian sex in harem games. Best practise is to just stay away from NTR and lez in harem games.
Alright so the tag girl on girl.. If you're going to have that, it should always be AVOIDABLE. Meaning, the player decide if he wants the girls to do lesbian shit. Meaning girls not doing shit behind his back. Harem fans are fed up with girls lezzing out because of reasons in harem games, and are now avoiding games with forced lesbian in it too.
Also, since you seemed to have changed your mind about NTR (FOR THE BETTER) best to keep your word and be transparent about content.
We might have just saved you a shitstorm when you had NTR planned in a HAREM game, which would have resulted in your game being blacklisted by harem fans, and you.
Harem is as easy and simple as they come.
Only complete speds mess it up by adding controversial crap fetishes into it that conflicts with the whole harem vibe of the game.
And if you think adding NTR was going to get you some extra dough, you are mistaken as well. Just harem and NTR do not mix well. It's legit oil and water.