First, a Stuka at a GV base guarantees no Tiger II will show up at its GV spawn at any point ever. No more offensive use ever.
I have seen a Tiger II drive off concrete exactly twice in my Aces High career. One was me, the other was somebody I killed with a Firefly.
You GVers are the biggest group of risk adverse players in the game, and you get more special treatment then any other group in the game too.
You get a commander who can survive being strafed while sticking halfway out the turret. You get reduced icon range, magical boxes of insta-repairing supplies, Star Trek transporters to take you directly into the fight, and the ability to sit on concrete, score kills, and instantly tower out when you see a bomb/tank shell coming towards you.
I think giving players the ability to spawn IL2's/Ju87G2's from vehicle bases is perfectly reasonable considering all of that. I would go even further and say it would be reasonable to remove aircraft icons for GV's, place a fifteen second delay on the .ef command while in a vehicle, and add a thirty second timer to vehicle supplies.