I can certainly lower the crater airbases, 6K is too much of an advantage over any other airbase on the map anyway, none of which are higher than 2K.
The central airbase is an interesting idea but sadly it won't work for an MA terrain. It would have to be initially assigned to one of the three countries (a fourth neutral country would introduce a whole load of other issues). The country that initially owns it now has one extra base than the other two which unbalances the victory conditions for the map. So OK you give the other two countries each an extra base somewhere else on the map. This is also unfair as the central base is far more likely to get taken than the other two bases. There are rules that say an MA map must be fair to all three sides, must have equal numbers and types of fields and a central base breaks these rules.
BTW there are loads of other rules and guidelines regarding MA maps, far more than special event maps. If anyone's interested I once wrote a BBS post about it
here. Its pretty old but should still be mostly correct.
I am not a fan of making the crater V bases uncapturable, griefers would still kill the hangars or bomb the GVs from the airbases. I have doubts about whether Hitech would allow it anyway (I vaguely recall someone else's MA map idea getting rejected for uncapturable fighter town or tank town bases).
Can I just state here that don't care much about tank town or fighter town being permanently active but I do care about all players, both pilots and GVers, having fun. Fighter town and tank town is just useful to kick start the fight when the map first appears. However the important thing about this new layout is that even after all the crater bases get taken by one side each countries' GVers or pilots will still usually only have three spawns or three nearby airbases (plus occasionally a fleet) to choose from. This means either two spots on the ring of airbases, two on the ring of V bases and one on the spokes leading to the crater. It is this concentration of the few available players that I hope will generate a fight even outside of peak hours.
Other QOL improvements I hope to make for GVers is to move the airbase towns nearer to the airfields and reduce spawn point to map room travel times. Also I'll try to create kill zones between the spawns and the map rooms where a defending GV can ambush incoming enemies. Finally I will clear spawn points and the routes to the map rooms of excess trees.