Imagine what our GV gameplay would be like if AH limited us to cross-country speeds... 
MH
And this has been debated before, a few times in fact - road speed is the speed we have for vehicles and 99% agree not to change it due to the time and speed problem, however if we added natural resistance such as rivers and weather then they should be slowed to appear realistic.
I personally agree to keep all vehicles as their road speed only, only thing is I wanted to add natural barriers like muddy fields for example to bog tanks down.
However without weather it simply wouldn't work as you'd have a weatherless map and all sudden muddy fields, so it simply wouldn't work. Maybe in due time when weather can be added, for example Snow and Rain to cause natural barriers for GV's. As someone pointed out, I'd like to see a Tundra map so we can start using some of our winter skins.
Its been discussed about weather as well, it simply won't happen anytime soon - we have it actually, I flown in scenarios and Snapshots with weather turned on, its actually quite interesting.
