It must be addressed by something.
I am not sure this is the case.............. any more.
It would be nice to think that reducing the majority side to higher ENY ac balances things from a players perspective....... statistically across the three country set this may be the case, but in terms of individual (and local) game play there are much greater levels of miss balance in play that mask this influence on game play whilst denying access to ac.
Local combat to an individual can be unbalanced with respect to quantity of attackers, E state, base attrition etc in both positive and negative ways regardless of which side is enjoying an ENY advantage. Indeed the local numbers game far out ways any ENY bias.
Combat is localised throughout terrains such that if one battle isn't any fun then many folk go and participate in another.
So I do not think it
HAS to be replaced.
However if there was a need to replace it I would use a system that did not deny access to certain ac totally. A more dynamic perk system in use across all aircraft would enable players to use any aircraft provided they had the perks to deposit.
This "perk currency" would then be in play.....
It could be used so many ways.
It could be used such that (as now) the perk deposit is indirectly proportional to side balance.
It could also be used on a side influenced supply and demand model. (if everyone on one side is using Spit XVI's then the deposit required in creases). {hmmm missions??}
But the core point would be.... don't deny access...... just increase the deposit price.