shoehorning too-large events into too-large-but-cheaper space
Do you mean too-small-but-cheaper space?

Let me propose a compromise, one which has probably been done before. Rent space where the main event hall is too small, and pipe the proceedings into overflow rooms. The technology was there at Denvention. Also, arrange to broadcast the main events on one of the channels at each hotel. Not as easy, but it can be done. Finally, webcast.