To edit the looks of US airfield, you need Gmax, RenX, and FinalBIG programs
here for modelling tutorials, utilize google, it does work
To dedicate the airfield to 2 units only, maybe 2 RiderChangeContain modules could work, I'm trying to work how it works out myself atm, but to dedicate specific slot, not sure if its possible.
As for the closing hangar and stuff, I think you could mix the
KeepsParkingSpaceWhenAirborne = No
from JetAIUpdate module, and give both c130 and b52 a weapon that has the requirement of docking at an airfield to reload (some piece of code in weapon.ini, look for it in jets' weapons). But this means any plane of the same type (IF riderchangecontain works) can land instead of the 1st one whenever he wants. Also, from what I remember, hangar doors open the moment you assign the unit to an airfield (right click on it, or unit is out of ammo).
This game is too old for too complicated stuff, maybe annihilation will have another solution 🙂