Alright, how does everyone upload pictures here?
The last solo game was because... I put a lot of emphasis on the setting, and those who haven't played at least the first part of the game won't appreciate it, which is understandable.
In short, Solovey is always on Elizabeth's side in the story because he has a "program" for that. The player controlling Solovey should want to save Elizabeth, not win for himself.
As for the powers... 6/4 can easily become 5/5, but if you have more specific suggestions for balancing, I'm listening.
Added after 22 minutes
For a game with 13 players, Tox just had an optimal setup: 8 townspeople, 4 Mafia, + a serial killer.
Added after 34 minutes
Or, here's Master's setup: 8 townspeople, 3 Mafia, + a deception role (doesn't kill, but wins with the villains), + a serial killer. That's also an interesting option.