My question to the op would be why? Why do we need an extra large field?
The last time you tried to take off in a heavy Ar234/B-29/B-XX in the MAs without using auto-takeoff was, when? Not saying everyone needs them or will use them, but for select purposes by a select niche of players, they will be heavily desired and saught for operating out of.
Most nights I like to fight and wouldn't need them, but a couple times a month I might just want to do a really long high/alt bomb run to a strat while listening to music and sipping on a tasty beverage. I will load my buffs up heavy for the mission and go for my 1-2 hour sortie. I know there are others (though not a majority) that do this primarily as their source of entertaintment and enjoyment found within the game.
My intention would that it would promote combat. Think of it as a focal point of combat near the front lines.
I am not trying to promote mega horde vs mega horde either, although this might be a possibility. I am simply trying to find a means to help promote aerial combat by giving both base takers and furballers a place to do battle.
I like it, but don't see how only having say three like you originaly propose would do anything to change the current environment which is most players looking to fight don't have many choices and most mass at the same location. There are already many bases that are focal points and keystone objectives to taking a group/nest of bases, go load up and study a map up in the MAs and it wont take long to find one with the V-Spawns turned on. It is rare, but once in a blue moon players do organize a sneak of one of these bases with the intent/incentive being that taking it will secure the entire region of nearby bases shortly thereafter.