I've been thinking of several ways to do Sorcerer without a single designated GM, I had this idea:

Outside of conflicts with demons, other PCs and the elements of the Bang or Kicker a character is working on, the game is freeform controlled by whoever wishes to narrarate.

Your demon is controlled by the player on your right, and your kicker is controlled by the player next on your right.

So each player assumes three roles. Sorcerer, demon and GM.

This has the possibility to get pretty heavy. If such would be the case, the game could be run so that each session, it is focused on one Sorcerer.

The biggest part of this that would need to be written out would be the constraints of control over "Bangs". Perhaps you could have a list of people, places and things that the Bang is concerned with and are therefore controlled by that player, they would also be the ones to call Humanity rolls for things the character does to deal with that bang.

Another optionial idea, If there's a character that you don't have a demon belonging to, you can try to summon a demon with him as the controller, and if there's a player that you don't have an active Bang occuring to, you can make one for them.

This has alot of nice potentials such as a more flexible game group, with more people or with one person missing without it being a big deal. Think it could work?