Perhaps ENY could be assigned to individual Bases rather than to whole teams. The Dar-Bar keeps track of team plane-count by sector, so bases in that sector could have ENY calculated by the sector ratio instead of the Team ratio. This could be extended to bases within one sector to keep adjacent bases ENY-ed. This would create in some situations where bases would have different ENY values being assigned based on what was happening around them..or a 'conflict in ENY, but this can be easily addressed by Averaging the different overlapping local ENY calculations.
This might help the lopsided fights where a TEAM with less pilots overloads a few sectors and benefits from ENY even though they out number everone at those bases.
And if a Pilot wants to fly 2 sectors to a fight just so he can have his P-51, so be it.
I honestly think this would address the real gripe with ENY, which occurs when you're upping at a base where you're outnumbered 2:1, 3:1 and you can only up in P-40 against the hordes of P-51, Typhs, and D-9s, because scattered around the board your team outnumbers the other team. This is what ENY is trying to address but actually doesn't.