I've been following this story for a while now, though this is the first time I've posted a review. This is definitely the most in depth and developed lemon fic I've ever read and I really enjoy it.
I saw Sage's Corner post and I like the idea of bringing in fem. Orochimaru, it would seriously put Naruto's ability to reconcile his lovers' differences.
As far as more ladies to bring in I would recommend the kunoichi from Basilisk for sure (I would like to see all of them but even just one would be nice) and Tenzin would make a great villian for any future arcs, if you really wanted to go crazy with it you could bring in some characters from Manyuu Hikenchou, you could change Chifusa's goal to easing the conflict between the nations and thus being a natural ally to Naruto.
I would also suggest Rias Gremory or Souna Sitri from High School DxD and Azula from Atla (though that's not actually an anime) to be nobility since Naruto doesn't have much influence in those circles outside of Koyuki and now Haruna. Also, since the priestly class seems to be developing into a faction unto themselves you might consider Akeno Himejima (HSDxD) and Kikiyo from Inuyasha.
Mikasa from AoT and Mikoto Kusanagi from GitS could be kunoichi from Iwa since its mountainous and they have a habit swinging around like spider-man and jumping off tall buildings respectively.