I wonder if we really need balanced maps. I mean perfectly balanced. Most of the maps on WoT is symmetrical probably just because of that. It's kind of boring.
What wrong would happen if map were asymmetrical? For example one side has some advantage when attacking, and the other when defending. Like some rocks on the one end and bushes on the other. Of course I don't mean total lack of balance, but 5-10%? In the long run everybody plays both sides the same amount of times.
There is a risk that some tanks would be OP in some conditions, but tanks are chosen when map is not known yet, so I guess it's irrelevant.
There are already modes of play (attack/defence) which give similar experience. So "unfair" maps wouldn't be dramatic change. Instead it would open a way to some creative tactics.