I not following you... how would that affect attendance? Are you saying that people won't show up unless they get to fly the aircraft of their choice?
I would certainly like to see more than 2 different aircraft in use... in that situation, you would see, for example, a squadron of 4 people in Il-2s, and everyone else in La5FNs. I'd prefer to see squadrons of Il-2s, Yaks, La5s, etc. The scale could be very simple, and it would be easy when the TOD was announced and the squads for each side listed for the CM to say 'Allies must use X number of different aircraft types, Axis must use X number of different aircraft types'. I think that would be very simple.