Identify mistakes in rulesets that led to imbalanced mafias.
Require people who wish to sign up for mafia to present a ruleset, reviewed thoroughly by multiple people to avoid those mistakes, with some form of playtesting heavily encouraged.
Consider simpler rulesets, based off ones already tested and balanced.
Have at least two weeks between thread posting and game starting for rules to be reviewed by the public while the game is in center focus.
In order
1. This is a bit difficult to people who have not run one, or people who are making their own for the first time. While that is no excuse, oversight should be taken with some sympathy. I think people are trying too hard to be unique, some of the classic mafias run in the past were run using a fairly worked out ruleset and it made things fair (I can see however, how this could take away from the excitement)
Perhaps, this thread could be made to showcase some past mafias that were very successful balance wise, with explanation, and perhaps even show the previous two mafias with brief commentary on what was, and wasn't balanced.
2. This would drag times down to a vast degree I feel, though it is an important idea. I feel I touch lightly on what I would do in the previous response, but still, even if a system with so much input isn't used, it is important to start balancing before the game goes live. Perhaps in order to be selected for the next mafia, you must have a ruleset up on your signup post within a few days of the last mafia going live?
3. I touched on this in response one, and I agree wholeheartedly, despite my desire to make a unique mafia myself
4. I touched on this in response two, I feel this two week period can be shifted to around the last mafia going live. Maybe that's unrealistic for the person who is going after math, but certainly after that person it should be easy enough to have some rules posted in advance.