The idea, in and of itself, is pretty cool IMHO. The only problem would be software comparability. If the file is being sent back and forth between cartographers, I would suspect that they would have to be using the same versions of the same software to avoid file conflicts/corruption's and what not. Still worth considering though, it would be cool to see what partners can produce when working together, though if John and Misty joined forces, we would all be toast.