I'm still fairly new to FSO (this is my fourth), but in discussions with others I was encouraged to present this idea towards helping to better balance the sides at the last minute, if necessary, due to actual turnout.
I know side balancing is difficult to do, but I have an idea for last minute adjustments. It could be set up when assigning sides such that, one large squad, one medium and one small squad are not assigned to either side, but are designated as "transitionally available" (a "Taxi" squad, if you will) for that Frame (or Event). Being initially unaffiliated to either side they would have no orders issued in advance of the Frame, and would not know the strategy of either side.
These squads could be moved (just one, or two or all three), as necessary to which ever side needs the pilots so as to reach near proper balance as defined for the Event. They would, if at all possible, be assigned as a squad (so they would at least fly together) in the last 5-10 minutes before the start to a particular squad on their 'new' side, who would impart the plane/loadout and lead them in the mission.
Squads would rotate each Frame (or Event) being in the "bucket" as one of the transition squads. As a Taxi squad, they will know to be prepared to join up quickly on whichever side they are assigned.