AAAaanyway, I woke up thinking, "Why not?"
Some background--my church will believe anything. We're a hodge-podge collection of spiritualities, including pagans and athiests and Secular Humanists and Christians and...what have you.
Mage: The Ascension is a role-playing game like Dungeons and Dragons, but instead of a game of fighers, wizards and killing monsters, it's a game of magical philosophies that can change the world. You can play a Catholic priest that can lay on hands, call down fire from heaven, and even raise the dead. You can play a Wiccan-style witch who can read fortunes in cards, call up a storm by tying knots in rope, or see through the eyes of a crow. The game uses voodoo, shamanic spirituality, neo-gothic hodge-podge occultism, Eastern philosophies, mad science, ceremonial Hermetic magic, alchemy and other magical styles/paths for its backdrop.
So...why not hold this as an event sponsored, or semi-sponsored, by a Unitarian Pagan group? Granted, there are elements of sacralige, or at least irreverance, but it'd be a good way of letting people play out their ideas of Magick in "real life," and a huge portion of paganism is developing your mind's eye, there's no shortage of let's pretend at work there. Since this would be a live-action game, there'd be an element of playing out rituals, too--though in a safe virtual space. And anyone who doesn't think there's a massive cross-breeding between role-playing gamers and pagans borders on the delusional.
Another element of Mage: The Ascension that lends itself to UU'ism and Paganism is the idea that 1) your own beliefs shape the world, and 2) more importantly, shared belief and the people around you are powerful and useful. That encourages an outward focus to the characters' activities.
The hardest part would be reserving one of the church's large double-rooms for six hours. Yeesh. But it might be worth it as a way of showing younger, weirder people that UU is a different, "harm none but do as you will" religion.
I also had what I think is a fantastic way of balancing out storytellers--the people that run the game and help steer the world--with players. Divvy the game into three-hour chunks (may not be strictly necessary). Anyone that runs a game for three hours has the right to commandeer a storyteller at the next game for an hour for a personal plotline or up to three hours for a small or large group scene.
This would encourage storytelling, but it would also encourage that most essential part of a Mage game--plots driven by the players and their characters.
I may blip this message to Hill Woman and her husband, Yew Grover. It's an interesting idea.
Obvious problems--offending people's religious sensabilities. The only way to deal with this is to remind everyone "it's just a game" and "you aren't your character." I'm not sure that potential (and in fact guaranteed) problem is large enough to overcome the basic good-ideaness of this.