What I would like?
Huge teams - talking 100+ each side
Persistant, large maps - thinking city sizes, something that wuold literally take hours to get across on foot.
Health/Armour with repair/medic packs/guns - I hate all these health regen games without good reason, halo gets away with it as a sci-fi setting and shields thing, but even Halo:CE had a healthbar that didnt recharge under the shield.
Vehcles - I love combined arms combat, and want Choppers, Jets, Tanks, Buggies, Boats, Ships, Cars and giant robots! Sci-fi themed would make it all the better!
Locational Damage - More a vehcle thing, but headshots would count too I guess, I want a rifle to do fuck all to a armoured car, but shooting the tires can help slow it/make it difficult to control. At the same time, shooting a rocket at a fancy tank and hitting the gun, won't destory the tank, however it could destroy or damage the weapon so that it gets jammed facing one way, or slower firing. Planetside1 did this great with BFRs (the only good thing about them really) with precision shots from small arms able to disable their flight/weapon/shield systems, so that the big guns could rip the armour apart.
Destructable Terrain - BC2 has spoiled me somewhat that I love taking down buildings, although it still needs some refinement, such as only killing people that it actually makes contact with, not just everyone inside the "zone" of the building that collapses.
Commanders - Someone that either earns or is voted to lead a team, giving them abilities to spot enemies, draw battle plans, give orbital strikes/artilary and generally be playing a RTS while all his units are playing a FPS!
So all in all... I want Planetside 2 to be released already, with the addition of Destructable terrain and locational damage...