RE: Vote or Vig
I can see a breaking strategy assuming all towns are cooperative (scums don't have to cooperate as it only hurts them i.e. not cooperating means scumclaiming by game design)
Also I discounted the cases where the game ends with scum win at the end of pregame as that's the most trivial case. And there's a way to guarantee that never ever happens.
Breaking strategy:
At the beginning of every day, especially D1, check who can vote by forcing everyone to put a vote down to all different players. That will make it clear to see who's voteless. All town agree to not vig that night, agree to all choose to vote the next day (and every day).
Some factors determine whether town will 100% win or not. But even the "not" scenarios are very heavily town favoured. I can't even think of a scenario where the win rate is close to 50-50. I believe there is none. All possible cases are significantly advantageous to town.
Solution:
Mafia always have votes AND faction kill.
If scums have to choose between the two, making the factional kill hurts their win rate. The breaking strategy revolves around voteless being a necessary consequence of getting the faction kill.
There aren't many scenarios where utilising the NK doesn't outright lose them the game. And those scenarios are the ones where game potentially ended at the end of pregame as scum win.
There are some other patches I could think of but those more or less contain loopholes that practically nullify them. (Or the game becomes a bit bastard.)
I didn't explain the details because it would take a sizeable table to cover all cases, but there are too many town 100% win scenarios and only a tiny small chance of scum's best case scenario which is still a 6v2 NK-less game. And scum isn't in control of making that best case happen anyway, it's a combination of collective town blunder and perfect scum play.
The game can be absolutely broken in queue even before game begins by designating 4 people to vig (and if they draw scum they're free to do whatever they want). I don't know if that's against the rules but just saying.
P.S. If you don't get why that's a breaking strategy, PM me and I'll come here and explain better (I might need a video or a massive table to do that though =P)