Plugin Request: Unlimited Sub/Child Users

I am hesitant to ask this, since I don't know how much interest there will be for other people, but I would like to see a way for members/users to create other users beneath them, as many as they want.

Let me make an example so it's more clear: I am trying to make a site for authors so they can develop their characters, so it would be great to have it so their characters can interact with others, sort of like a social network for characters. In this way, you'd be able to visit the character profile, and you could comment or post stuff as these other characters, but while logged into your main profile (sort of like how Facebook does with posting as a page).

This could further be done where maybe you limit the number of sub accounts for free users, and raise the allowed amount for premium users.