Been thinking about this some. Here's an idea I came up with, I'll call it "Come From Behind Mafia" inspired a bit by Innovation, Inc.
So, as in other cases you have 5 players, 3 scum, 2 town.
-The 2 town players are secret (1-shot) double-voting, doctor-vigilantes.
-The 3 scum are secret (1-shot) *double-voting mafia goons, with daychat, with a special rule (*) on their secret vote that it cannot be on the same target as their actual vote.
-Secret votes are cast by PM, and are included in vote counts, but not who cast it.
-Simple majority of the maximum votes on a player are needed to lynch...so that's 4 day1 (7 vote max on any given player), and could be something different on later days depending on how things play out.
Otherwise this runs as per normal mafia rules.
At a basic level, if town can recognize their fellow member, then they can lynch scum, and protect each other at night while killing the remaining 2 scum. If they vote for their fellow townie, scum can quick-hammer and win. Scum can pretend to have double-voting powers by coordinating secret votes, but they cannot lynch town unless the townie helps.
There are a variety of situations that could come up depending on what combination of lynch/no-lynch and night kills happens.