Anyone thought of using 'Mythic GM Emulator' with Mortal Coil?
Here it is: http://www.mythic.wordpr.com/page9/page9.html
Mythic is an interesting system, but it is percentage based. The "no GM" feature is basically asking a series of questions, working out how likely they are true and then rolling for the result.
Not exactly compatible with a diceless system.
The best way would be to work out the likelihood of something and just choosing the best (most interesting) result. If a player really wants something unlikely to happen, they must spend a token (more than one if it's really unlikely).