I recently suggested a similar scenario in this thread.
http://www.eccie.net/showthread.php?p=499967#post499967
And here's a couple main paragraphs...
"An interesting option, that may have been discussed previously in one place or another is to organize not so much a GB, but an actual orgy/party with the ratio of men to women stacked to reflect that women's libido's almost always exceed the capacity of male performance.
One scenario: 6 guys, 3 women...a 3 hour window with each guy donating $$$$$. Each provider would exit with 1K, and there would be enough flexibility in the configuration that options for GB like play are there, as well as more basic pairings. I'd suggest that having providers who were bi would make it all the more viable. I think the weak link would probably be finding 6 guys who would be comfortable in that scenario."
I added a few caveats in the original post...also, with that many people involved, I have the feeling that 90 minutes will feel rushed. If that was the consensus, I'd still be game.