I can somewhat understand the logic behind tank stopping trees: They effectively stop planes, too.
The easy solution would be to make all trees penetrable in the same way the flowers are. For tanks that would work to a degree, just drive through the trees. The problem is, how to make the same trees not to allow planes fly through them. That would allow hiding a bunch of C47's into the trees which definitely would add an unrealistic effect. Not to mention surface fighting and NOE attacks. Also, that would allow shooting through trees by simply pushing the barrel through, the rest of the tank being hidden. Talk about spawn point camping!
So holographic trees are not the solution here.
Another solution would be to have a scale of hardness for every type of object in the game. Thus a house wall should be harder than a tank, which should be harder than a tree, which should be harder than a plane. That would work if all objects had a simple "bubble" for damage modeling. However, there's variables like armour angle and thickness, speed and direction. Planes and tanks in AH have a realistic damage modelling, the strong and weak spots being as realistic as possible for a game. Thus it's possible to kill a tank with the 9 mm pistol of a bailed pilot by shooting the tank driver through the peeping gap.
Of course everything can be coded to simulate the real world. There's a reason why real pilot training simulators are beyond reach of the average cartoon pilots.
