The Exact Game Mechanics
The first phase is Day 0.25, in which all twelve players may speak and vote for one player whom they wish to revive. This is done with lynching mechanics (simple majority). Once a decision is reached the game progresses to Day 0.5, in which all players must again revive a player, but obviously not the same player. Repeat on Day 0.75.
After this, 3 players will be alive and 9 dead. If at this point the mafia outnumber the town then the mafia win. If not, the most likely outcome, the game moves into Night 1. Any and all night choices are carried out by only the players who are alive, and they may only target other living players unless their role explicitly says that they may target limbo players as well, except that no killing will be allowed on Night 1.
In the morning, Day 1 begins. All players may again speak, and again the aim is to revive a player, but now only living players may vote. At the end of the day a player will be made living and Night 2 begins.
This continues until either side's win condition is fulfilled, and they are:
Mafia: More living mafia than living town players.
Town: Either: all of the pro-town players revived (it is not required that all pro-town players survive after being revived though), half of the total pro-town players alive, or all mafia dead.
Also, to ensure that you cannot determine who is mafia based on when nightkills start to happen, I have assigned each member of the mafia a randomly generated value that determines whether they may or may not kill on the first night after they are revived.
At day you may use any methods to get players revived that you would to get them lynched or saved from lynch in a normal mafia game. This includes claiming, if you so desire.