If the convention center allows it, I would vote for partially sectioning the rooms off during regular play and then opening them up for the Special. I know there's a worry about headache for the HQ table, but it might actually relieve the stress, as I know there were a lot of musterers who kept coming up (I was one of them) when HQ wasn't quite ready to let generics in. Sectioning would probably help keep the musterers in their own little area until they're called on by the high and mighty folks at HQ.
That aside, I'm also down with Tim's crazy idea of making some form of PVC tubing apparatus. Perhaps each player has one tube over their ear and one over their mouth, and it connects everyone together so they can hear and talk, but just among the group?
Ok... maybe I shouldn't encourage Tim!