I'd just point out here that hiding in a hull-down position in an ambush spot looks so different from the ground as compared to FROM THE AIR that it's not even a valid comparison. How things look from the ground vs how they look from the air never match up. You can hid from air spotting or you can hide from ground spotting, but they are mutually exclusive.
Tanks were not invisible from the air, and should not be invisible in this game, nor should they be undetectable just to give an artificial leg-up to GV drivers who want to camp with impunity.
Get in, get the job done, and move on. This whole obsession with getting the camp going is bad for GV gameplay. Hell, I once got 23 kills on an enemy field -- no not shooting into the VH but nearby waiting for targets to come out -- and it did nothing. It was me being a jackarse and I can promise you I didn't do anything to help the team for it, didn't really have a sense of accomplishment other than "how long will this go?" and it definitely wasn't rewarding in the scope of gameplay.
On the other hand, I've died 5x trying to push a GV into an enemy field and clear the town, but my deaths told the tankers right next to me where my killer was hiding and they killed him. Despite multiple deaths I made it and guarded troops as they went into the map room. Pushing forward, keeping on target, on objective, even though I died many times was far more rewarding than just camping to artificially inflate a score.
I've done both. I've pushed forward. I've camped. I've tried to break through and been camped. I've bombed, I've strafed, I've spotted without engaging. GVs don't need invulnerability. They need a kick in the pants to keep on-mission. Being spotted is that kick. They should not operate alone, but with friendlies overhead. Before HTC killed GV icons I'd spot for tankers in battles to take fields once I'd cleared the area a bit. Tell them where to adjust rounds and ranging tips. Now, there's no point because you can't see them. It's a double standard, and those are innately unfair and unsatisfactory.