Actually, I was thinking - it might be better if there weren't any airfields at all on the center island.
That way, if a few players from a country did sign in and find all 3 bases belonging to another country, they could up a strike mission, take a vehicle base, and have more than the usual minute or two before being subjected to the first airstrike. It would promote defenders jumping into GV's to defend instead of relying on air strike capabilities from the airfield 60 seconds away to recapture the base. (Which makes the ground players happier because there's more incentive for a ground war.)
And because there'd be no close air support to either defend (or take) GV bases, doing either one with aircraft would require a little more planning, be a little harder and a little easier to stop - and once again promote the use of ground vehicles because they are closer and easier to re-up if you die (which would again make the ground players happy.) And without some ground support, keeping the field if you took it solely with air would be highly problematic - unless you up GV's to defend it once you take it, the guys you took it from would simply up a tank and the required number of M5's when they see the writing on the wall, run off the field a bit, and once it's taken- retake it - probably before the C47 could land.
Also, without airfields, there would be much less strategic importance to taking the island from the point of view of those who play field capture in the first place. It would no longer give them strategic airfields from which to strike across out the rest of the map. This means the ground players would be a lot more likely to be left alone until the end game because the vehicle bases are easier to take and retake - without airfields on the island, I *think* they'd be more inclined to be ignored until the final hours of the map, since if you try to take them before you are "nearly at reset" you're going to be spinning your wheels trying to re-take them every 1/2 hour.
Without airfields, I think that you'd see that final, bitter battle often being fought over the island, as the "almost losers" take and try to hold the GV fields on the island to prevent the reset and the "almost winners" trying to take the that last field there because it's harder to take an airfield, which means that the GV players would have a siginifant strategic role in the end game.
All in my own very humble opinion of course.
