Ok... so as with all games that allows you to fly around, one can only wonder.... how does every player character already know how to fly a airplane AND a helicopter? gets you thinking no? So i figured a good class to add would be a Pilot class, which would have special abilities to use while piloting a chopper or plane, like countermeasures for S.A.M.s and such, explosive bullets for the miniguns, increased health for the airplane/helicopter and such, it would also have SMG/Side Arm abilities like increased damage... but as a pilot it would be locked to having only ONE primary weapon from the SMG tree and one side arm.
im sure other ideas could be mentioned for new abilities for such a class but yeah, thats just what i can think of for right now lol