This reminds me of doing shows and events 10 years ago. We used to provision our own Internet circuits for just the event to get around bandwidth issues.
So if the issue is bad enough, provision your own UFB circuit. You might have to commit to a 12 or 24 month contract to get it, but that is just part of the cost of the event. You'll also want to book the circuit well in advance. If they can't get you UFB try ordering a VDSL circuit.
You'll need to do this with the co-operation of the people who run the facility.
However, the first thing I would do is ask the venue if there is some kind of "premium" offering you can buy.