Shooting from the hip here.
Take the idea of Early War Arena, Mid War Arena and Late War Arena and roll them into 1 arena.
The Terrain would have 3 separate zones Early, Mid and Late that are separated by a considerable distance to discourage flight between the areas.
Instead of perks use for individual sorties, perks would be used to unlock different aircraft in each zone. Perks could be spread over the three zones so you could fight in the early zone and gain enough perks to unlock an aircraft on the late war zone or vice versa. Every aircraft would have to be unlocked except for the initial opening set, Hurri I, I-16, Bf 109E4, etc.
Each zone would be capable of resetting the arena, so the fight could hinge on any of the zones.
Just an idea, maybe it has been proposed before, but things like these usually pop into my head every now and then.