I've given a little bit of thought to a possible plane limiting system.
Each player has thier own hangar, what other people do with thier planes has no effect on it. The player has a limited(or unlimited for high eny planes) number of aircraft available to them, which rebuild over time based on thier countries strat, and the plane itself. The rebuild happens wether or not they're online.
Every plane, including the perk planes would be available from this hangar. If a player runs out of a certain plane, that plane will be available for a price in perks. The price of the perks would be based on how much rebuild time is left untill the next plane is ready, and the plane itself. Using something like this, newbies could get the opportunity to fly planes like the me262 on occasion, without having them taking over the arena.
A system like this could offer a lot in the way of helping to slow down suicides, and also offer a way to have the lesser flown planes flown more often. (ENY and the perk system are currently not a reward for it)
Someone else, I forget who, mentioned the idea of having fields hangars disable certain planes. i.e. A field with 3 fighter hangars, losing one, would lose a random third of it's fighter types. It could also be randomly spread out to disable roughly the same quality of fighters. i.e. each hangar being killed would knock out a few low eny planes, a few medium eny planes, and a few high eny planes, rather than a completly random selection.