Karin and Yuzu, Ichigo's sisters, could be part of the harem in a non - traditional way. Their connection to Ichigo and their own budding spiritual powers could create some interesting family - like relationships within the harem. Uryu could also be there, his Quincy abilities providing a different perspective. And a new original character, an arrancar with a mysterious past, could be added to the harem to stir things up.
Tatsuki could be included in the harem. She's Ichigo's friend from school and her tough - as - nails attitude would contrast with some of the other more spiritual characters. Yoruichi could also be a part of it. Her experience and powerful cat - form abilities would make her a valuable and interesting addition to the harem. And let's not forget Chad. He could be like a protector of the harem, with his own brute strength.
Rukia could be one of the characters in the harem. She has a long - standing relationship with Ichigo and her own strong spiritual powers. Orihime could also be part of it. Her kind - hearted nature and unique abilities would add depth to the harem dynamic. Another potential character could be Neliel. As an arrancar herself, she could have an interesting relationship with arrancar Ichigo.