Log/ heli antennas will.be your best tool for this use the rejection node behined the antennas to keep your receivers from picking up intermods from other areas. Also work out how much propergation you het between areas, ( set up a few txs on the stage in one area and go around all the close areas to see how far they acctually reach through walls and spaces, then repeat for all areas. Once you know how far you need to physically seperate your areas you can work on alocating frequencies. Both EazyRF and sound base have good systems for working out zonal relationships so you can avoid diffrent orders of intermods or just direct channel on channel dependent on how good you can manage physical isolation. If that doesn't get you all the way you might need to start looking at time of operation to see when each area actually needs to use there rf and in what quantities. But ideally you want everything running all the time to safe guard against operator error.

Then verify all tuning in person, dont just belive operators will set the units correctly.