They shouldn't be able to take out air support, in previous COD's only the LMG's were really effective and even then it took a while - on the other hand air support is so easy to get in this game.
As for the FMG's, I used to use them akimbo, they're in the game and it's legit, it's down to the dev's to decide if they need nurfing, personnally they are only really effective close range and as all the maps are pretty much CQC, they are effective on pretty much all the maps.
They would not be so overpowered on most of the maps from previous COD's and that includes MW2.
