I had an SDK parked near a town inside a thick grove of trees for some 20+ minutes once. The effort to drop the town failed to materialize (they were pushed back) but I had 4 planes buzzing around looking for me, trying to attack me. They had quite a hard time and 2 augered giving me kills.
Claiming they are still visible is one-sided myopia only the perspective that can't say one way or another: The tanker's perspective.
As one that has defended bases against rolling hordes of GVs, I can say for sure they lose icons quite easily in trees and are QUITE well covered against bombs guns and rockets with even modest foliage. Most tanks require a direct hit with a 1000 bomb down the gunner's hatch to do any damge, anyways.
Wishing for things that coddle GVs is foolish and clearly selfish. If you want it to be more realistic how about removing all spawn points? Make them drive. How about increasing fuel burn like planes? To make it worth taking supplies? How about modeling actual terrain instead of this perfectly flat full-traction world we have? In the real world going cross-country isn't that fast nor is it smooth and easy. You can't fire the gun while rolling either. Well, you can but you can't hold an aim on anything so it would be a random direction you fired into.
So, please... stop trying to give fake arcade powerup type wishes to GVs. Especially when they don't need it!