I'm thinking a new Theremin may be very beneficial to create for this purpose. It should have the following features:
[b]Wide Linear Note Spacing[/b]: I'm talking about one or two octaves in the span of an arm. This would make it easier to hit notes on the go, rather than the tighter tuning which can be beneficial for stationary playing. It will be adjustable, though, in case people JUST CAN'T get used to it, or their arms get too tired. Also, it should have an octave switch, similar to the EWPro, as to get the full tonal range while utilizing wider note spacing.
[b]Multiple Timbre Control Options[/b]: I think a lot of cool things can happen here! Imagine 50-100 Theremins on the field playing, with no other instruments, but you hear Trumpets, Tubas, Clarinets, Violins, Cellos, women singing...all you would need would be right there! If a Tuba timbre dude is out sick, give their sheet music to someone else in an overpopulated timbre group. Violin dude is now Tuba dude. Percussion may be tricky, though...unless MIDI is introduced somehow...
[b]Wireless Signal Emitters[/b]: There will be no need for everyone to lug their own amp. The signal will be transmitted to a sound booth and sent over the stadium speakers. All that will be needed are headphones for the musician's monitoring. They COULD lug an amp if they want, but it would not be necessary. All the sound could be properly processed in the booth, too. Soloists could be turned up when needed. High-quality recordings can be made of the performance for whoever would like to purchase a copy to support the event.
Anything I'm forgetting?