Where are the Traitor vigilantes?
*scum vig
Why aren't there more double-voters and hiders?
Doublevoter is the next best thing to an Innocent Child in a Normal game, just not as cool. (It doesn't necessarily have to be this way but the prevalence of Mafia Doublevoters is very low AFAIK.)
Hider
probably isn't going to make the cut when the new whitelist comes out.
Put two millers/cops/doctors in a game to see what happens.
This is good advice, though for obvious reasons everyone shouldn't do it.
Can you have a groupscum without a nightkill?
Not in a Normal.
Can you have two mafia traitors and only one member of the mafia?
I think that this can work while preserving the nature of the game of Mafia, it would be shot down for not resembling a Normal game enough.
Make a four person neighborhood and put no scum in it. What are people gonna do?
That depends; are they going to arbitrarily assume that they're all confirmed Town or that at least one of them is confirmed scum?
Everything you say and do matters. People will respond in ways you may never see. May those responses be what you intend.