What happens when the ETO or PTO or what ever arena is full?
Adjust the parameters based on usage and desired result? Parameters being set cap vs dynamic, single theatre arena vs multiple of the same theatre, single theatre arena vs sub-divided (eg. eastern/western front). Adjusting on the theatre/time period choices where usage shakes out so the most popular choice is a plurality rather than a super-majority above 90%. Or at least a slim majority.