I'm not sure about the necessity of abilities, but about guns, i'd say let's make it overly specific.
1. Is must have - autogun of some sort that fires bullets/beams, whaterver...
2. Some sort of refferal to those "abilities":
NC:
- AV Bombs. Just a set of two or four short radius AV bombs for an "ammo box" (assuming there will be such thing as vehicle ammo resupply).
- AA Sparrow rockets, that follow the out-of-sight target. (Assuming there will be countermeasures)
TR:
- 2nd pilot with a 360 degree gun. This concept will never fail for TR. Extra gun that turns the vehicle into a light gunship of some sort.
- Striker missiles. AA and AV, but your target should be in your field of view. Not exactly in your sights, but just infront of you. (Assuming there will be countermeasures)
VS:
- Changeable flight vector, that adds more flexability in flight direction change (Assuming there will be no hovering for aircraft)
- Starfire AA rockets, that act as VS bfr mortar, igniting the ground they hit, if not used in AA. Some sort of napalm rockets, like seen with C&C Generals MiGs. Can lock on aircraft only. Your target should be in your field of view. (Assuming there will be countermeasures)