well from my viewpoint, this is a mechwarrior game, and the gameplay supports mech combat. tanks and aero are good compliments to mech, but when they are the primary unit, then this game doesn't offer all that much that other games don't offer in better quality.
for example, if i want to play a game where there are fighters doing combat, why would i play extremity when i could load up ace combat or battlefield 2.
same if there was an all tank map, i would just load up a battefield game, and get tank combat at a higher quality.
thing is, this is a mechwarrior game, and most of the people playing it are playing it for the mech combat, if you have maps where mechs are of little use, then your going to get what is happening currently. people will turn off the game and do something else.
theres nothing wrong with having maps where planes are effective, but if you do that at the expense of mechs, people won't want to play that map.