Jaunary might be a good time, though there should be some discussion and spamming of the comms in the interim to drum up further interest and gather ideas. Because obviously we don't want to do something exactly like the xover_exchange, so we want to give plenty of examples of the kind of madness we're looking for. Your example of a Star Trek Mystery Spot is a good one. My own Big Damn Heroes is another, if I may toot my own horn.

So the general premise would be to pick a plot/particular episode from one fandom and use the world/characters from another fandom in that scenario, yes?

Man, we're going to need some killer manips... :-O