18 people would be 6 baddies and 12 Innocents- I think I'd do 3 Mafiosos, 2 Quarky Agents and 1 Grim Reaper for the baddies, each with their own win conditions, and then of course the 12 Innocents, each with their own roles, and the Innocents win by killing all the baddies. though it may be too hard on the Mafia since they still have some groups but with more Innocents (but more groups, with the groups separate...). If we keep 15 people, there'd be 4 Mafiosos, 1 Grim Reaper and 10 Innocents