I actually don't think that there are too many teams at Worlds, I just think that the venue is far too small. If the event was in an adequate venue, I would even be OK with doing away with at large bids, and just let anyone sign up. The bid system is complicated and adds unnecessary friction to the whole process, IMO.
I would also let Event Producers give $ towards "paid bids" at their discretion. The only limitation is that they have to announce the amount of and process for their paid bids ahead of time.