I like the idea of the turret on the tank! But, i think it will probably be a minigun... and that part of the tank that shoots.
For the um, platform, could you give a little bit more deatils?
For the different levels of soldiers, that's a great idea! Maybe more different "types" instead of levels.. like maybe a SWAT ragdoll? They could spawn with shields... anyways will keep brainstorming!