I'm mildly interested in this, simply for the challenge of it, but I've not had a great experience with collaborative recipe making in the past. I've almost exclusively designed my own recipes, sometimes using recipes I've found as inspiration or general guidelines, and I've never brewed a kit (at least not an AG kit).
When I participated in a community brew before, the beer ended up interesting but not very good--drinkable, but you had to have a real tolerance for weird. It was fairly universally panned by all who participated. So you have a potential here to create something fun to brew but too bizarre to drink... or you can create something entirely banal, and that's not very fun. As long as this recipe is created with an adventurous spirit but a heavy dose of reality and common sense, and a judicious blend of democracy (meaning the majority can overrule a truly off-the-wall suggestion if it clearly is not befitting of the greater good), then it could work.
My bigger concern is the suggestion that "you don't have to brew the recipe exactly as designed." If not, then why participate in this experiment at all? To me, the reason for this experiment is to establish a baseline from which everyone can share their experience and converse on it meaningfully. If we're all allowed to go off on tangents and change this or that in the recipe, what is the point of a collaborative recipe? Since the participants in the experiment are not likely going to be sharing their creation with all of the other participants, there is no frame of reference if you start talking about what your modifications did to the resulting beer. This isn't like a brew club meeting where you can take in your beer and get the collective opinions of your fellow homebrewers. The recipe is our "control," and it's our various equipment, processes and experience that should be the variables. An experiment like this is less about the end product itself and more about the perceptions of that end product--if that makes sense.
What I'm suggesting is that if you decide to change any ingredient in the recipe, that you don't participate in the conversation regarding the final beer. Certainly, anyone can brew anything they want, but if I'm going to participate in a collaborative experiment, it must be a true collaboration. Otherwise, I'll just go ahead and brew any old thing I want.
Thoughts?