From what she has said to us as Mikeneko, she wants an idol environment again. She outright told us she does not want "freedom", she wants managers to set boundaries for her and a professional environment with like-minded girls to interact with. I think she would be fine having Akari and Pikamee around, but they also don't fit what she truly says she wants in the end. (Going by Akari very clearly wanting to get away from restrictive management and Pikamee never selling herself as an idol in the first place)
As far as where she could go, you're right in that her options are not readily apparent and may not even exist at this point. One thing she has told us is that she would be willing to accept small viewer numbers as long as the environment was right for her in terms of professionally managed, no males, gachikoi friendly, idol activities, etc.
If she leaves, she will probably abandon the Nazuna model and fully act as Mikeneko until she manages to find somewhere else to reincarnate a new character into. She'll keep simultaneously acting as Mikeneko even if she does this though, from what she's implied.
The major thing she has going in her favor is her core donors are legitimately in love with her and will 100% financially support her for the rest of her life as Mikeneko, but that isn't going to materialize a corporation for her to join and do concerts with again on its own.