Nothing!!!
New planes,tanks,submarines what ever make no difference to the game. I'd rather see changes to the gameplay,maps and strategy to take it away from MA Quake and possibly make it interesting again. Not to mention the graphics and effects.
Always get these posts for new planes, so HT spend time on it release it, gets flown for a week, then stuck in the hanger with all the other queens as everyone quickly goes back to their late war BnZ ride for some Deathmatch, rinse and repeat.
And who cares about more tanks anyway, if you want to be playing around with tanks your in the wrong game.
...-Gixer