3 x lone mafia
1 x town cop
some amount of VTs (6-9?), possibly a miller
The cop is exposed at the beginning of the game, however if more than 1 scum faction targets a player they will not die. A variant with 2 people on each scum team is possible but it seems like it would be a bit too big.
Mafia must choose who to kill wisely, considering other scum motive's, also must try and get the cop killed when no one is else is targeting them.
Something would need to be done to deal with cross kills as they could break the game, maybe the scum could have a rock/paper/scissors type relationship. A can kill B but C, B can kill C but not A, C can kill A but not B etc...
In the rare instance that A kills B who kills C who kills A, it could be no death