Simple: A person acting as the chairman decides on the secret ingredient and venue, both of which are announced on Sunday. Participants respond with what they'd like to bring, and their ideas are approved on a first-come, first-served basis. This serves not only to ensure that not everyone brings custard (for example), but also gives the chairman some flexibility in crafting a menu from the suggested dishes. The tasting happens sometime during the next weekend, and dishes are scored on the standard scale. The overall winner becomes the next chairman.
More complicated: Same as above, but with a handful of people - no more than 4 or 5 - named as Iron Chef (Whatever)s. Here, people can not only gun for the chairman slot, but can attempt to unseat one of the current Iron Chefs by calling them out.
Yeah, I know, it's not terribly original, but we're not doing it and I think it could be fun. Now I need input!
If you're interested, last week I posted three pics to 7shots here, here, and here. The first was part of the Gloucester photo-set. The others are new-ish.