I know, but for now, Charlotte is the only one we have to invite (along with the guys: Josef, Ken, and Adrian). That said, I don't see why—aside from "given their personalities"—we couldn't invite characters like Alice, Samantha (whom we already met in *Starcon*), Toni, Himari, or Sofia, or have Amelia hang out with Anna; in fact, there could even be a story arc involving Anna and Amelia, despite their differences.
Just imagine the possibilities. Maybe creating more *Starmaker* accounts would fit better in a different game, but I can picture inviting more characters to hang out with Anna... if only there were more time and interest (both have run dry until the game finally launches on Steam).
Another scenario I would have liked to see—even without Anna—is a meeting between two girls, like the one between Emma and Katarina.
But anyway, I suppose there's no harm in dreaming that mods might be possible someday.