I think trees stopping bombs is gamey.
But in the MA, people do all kinds of exotic things to try and stop GVs. They strafe it with HMGs, drop bombs at super low alts, up a buff and spray the entire area with 42x 1k bombs, go crash into it... and when they die, they up again and repeat it until the GV is dead/disabled - and that's pretty much darned unrealistic and gamey, too, IMO.
So, considering the fact that trees and forests are probably the only safe haven from the onslaught of aircrafts(as opposed to the fact that in RL, aircraft were extremely inefficient and ineffective means to destroy GVs), I think the titanium roof-top forests are pretty much fine.