I've got an idea for a rather unorthodox mini-game. The reason I'm making this topic now instead of queing it right away is because I want to know what people think about it first.
It deviates from normal mafia rules, but it's pretty straight forward once you have read my crappy explanation.
The game is called Catch the Face Dancer. A "face dancer" is a creature from the Dune books written by Frank Herbert. They're genetically engineered creatures who can take on the appearance and voice of any human they encounter. This means that they can kill someone, dispose of the corpse and infiltrate a community with its victims appearance.

The game takes place on a discussion board (or something like quicktopic) specifically created for the game. Each participant makes an account there. The first difference with regular mafia games is that the game host, me, is the one and only bad guy.

At the start of the game, all that is known is that the Face Dancer is around somewhere, but it's unknown where exactly.
When the first night-phase ends, the chosen victim (let's call him "Harry") gets a PM message from me that he's been killed and that he must give me his account on the discussion board to me. He must tell me the password for his account there and promise that he won't try to log in himself anymore. I will use the account to pretend I'm Harry. After that, it's day phase and someone is lynched as usual.
In the next night phase I repeat what I did earlier on another player. In the morning following it, the corpse of Harry is found and it's clear that the face dancer has taken on another appearance. So, the corpses found at the end of each night phase are actually the victims of the night before that.
The "townies" will win once they correctly vote for my current disguise/account to be eliminated. To do this they should pay close attention to changes in writing style, etc- and some luck won't hurt either.

Obviously this game will only work if people act in good faith and if everyone who participates is reasonably active.

Thoughts?