There could also be some original characters added to the harem. For example, a mysterious female ninja from a far - off land who has unique powers related to dark magic. This new character could bring in new story elements and challenges for Naruto and the rest of the harem.
Tenten could be part of the harem. With her skills in weaponry, she could provide a different combat perspective. Ino, with her mind - transfer jutsu, would also be an interesting addition. Her sassy personality would create some interesting interactions within the harem.
Sakura could be one of the characters in the harem. She is strong - willed and her medical ninja skills could be useful in the story. Hinata is also a likely candidate as she has always had a deep affection for Naruto. Her gentle yet powerful Byakugan abilities would add to the group dynamics.