Think of it this way: You wouldn't park the jeeps inside the bunk houses, would you?
Even if there were jeeps, they'd be in the motor pool, which is represented by the VH.
Even if you had troops to drive them, if the jeeps were blown up en masse (a bomb in a parking lot will ruin them all), the drivers can't do anything.
Having them tied to barracks will just allow too much abuse from the system, allowing dozens of them to spawn and rush the town to stop a base capture, even though the base takers took the time to kill the VH. Not to mention the fact that a dozen of them all together would make a damned effective AAA screen.
Also, with the absurd number of barracks on every field (something like 10, or 12, on a large airfield) they would never be disabled.
Interesting idea, but it just won't work. It's too much of a gimmicky way to stop base captures even after the VH has been killed. My $0.02.