I'm a little concerned by this notion of trying to kill off one anothers characters, it could come to dominate the entire plot and certainly stunt characterisation - what would be the incentive for the next writer in the chain to develop a character they only intend to kill anyway. It seems like an unnatural plot device, geared against the entire concept of a story flowing of it's own force.
As to the editorship position, your suggestion seems like a good one Marc. I was actually going to suggest that all of us collaborating produce a short piece anyway, just to explore the world - then we can sponge the ideas from each conception of the World that we like best and ditch the rest. Certainly we could tie this to a competition to decide who should become editor. If I might suggest though, rather than having a vote of the other participants, perhaps we should have another member not involved in the writing of the story directly to make the selection.
Hopefully by this weekend I'll have finished a first sketch of the World as I see it; which I'll then e-mail around for ritual flaying. If everyone else then does the same we should have a pretty good grounding not only of our World, but also an idea of one anothers strengths and weaknesses.