2 mafia factions of 3 each, 3 traitors and a serial killer is 10 evils and 10 townies?
1 cop, 1 doctor, 1 jail keeper, 1 jack, 3 masons and 3 vanilla townies?
maybe a decent mixed setup (serial killer could be vigilante maybe, serial killer is a bit .. meh as a faction being totally alone, but could provide for some amusing playstyles i guess)
not necessarily this, but something like this, 2 mafia factions so we only need 1 investigator etc