I understand your concerns.. though the "big" population difference i see is during low-pop, when a side has 10 (15 max for what i ve seen) more players.
During high pop time, the difference tend to be 2-10% max : The only risk would be during low-pop, but as those sites would be huge, the most populated side couldnt set down the
others sides production factories...
ENY system makes many ppl log off, as they cant ride Top aircrafts : making ppl log off isnt good for a game imho...
A solution could be to deny perked planes only for the overpop side... The big factories system could be a cool addition.
Easy. The most populous side would bomb the least populous side's Top Aircraft factory into oblivion and deny the least populous side access to P-51Ds, Spitfire Mk XVIs and La-7s.