Wrong, technically. The harem jutsu actually does require the use of shadow clones, because the regular illusory clones can't use ninjutsu (like the transformation jutsu) while shadow clones can. It's one of the two unique features of shadow clones, and one of the only reasons they are at all useful (and not just a costly and potentially suicidal waste of time, effort, and chakra). If you tried to recreate the harem jutsu with regular clones, you'd have one person transformed into a sexy woman, surrounded by 16 duplicates of their original self.
Yes, but the use of the clones in this manner is what only a select few have been shown capable of, mostly Naruto himself and Konohamaru, but a few others as well. Regardless, it still stands that only male characters have been shown capable of using any variation of the sexy jutsu, including the harem jutsu that requires clones.
There are no males in the harem, or in the game at all, and as far as I can tell there are no plans for it. There's also the issue that comes up with your comment where not everyone can use shadow clones specifically and, in fact, nobody in the harem is known to be capable. This was part of the purpose of the first few words in my comment, emphasizing that only the regular clone jutsu was needed to graduate as the shadow clone jutsu is a very advanced form of the normal one that is even specifically forbidden by the village. That was basically the whole reason the village went on alert when Naruto stole the scroll for it in the first arc of the series.
This means that the MC cannot use Kaguya's perversion against her because nobody has something to trigger it like Team 7 had. There is only one member of Team 7 in the harem and she was the one on the support role in the canon battle against Kaguya, not the one capable of a variation of sexy jutsu.