Due to nature of the 3D urban battlespace, I believe that there is an important role for an urban assault support vehicle; an SPAAG based system built into a single, tracked, highly survivable, combat vehicle. The chasis would be based on an an existing, highly survivable tank design such as the Leopard 2 A6. The turret would use the same armour as the A6 hull (which is classified). The turret would be centrally mounted with aquisition and and targeting radar, IR and optical sensors which could be folded down and retracted inside the mid hull for urban combat, as these systems are easily damaged by small arms fire. They would fully deploy in the secondary AA role. The primary weapon system of the vehicle, mounted on either side of the turret would consist of twin 20mm Vulcan cannon with ability to elevate to +90deg and depress to roughly -10deg. This design would greatly surpass any other combat vehicle I know of in the urban assault role with secondary point air defence capability, in line with the far less mobile C-RAM.

Also, the the ability to fire HEI and frag rounds, an enemy attacking from a position say, in the third storey of a building could either be blasted by shrapnel or have his weapons cache taken out by the HEI rounds. The rapid fire of the matched 20mm cannon would ensure a quicck response and a high kill probability. In this mode I'm unsure as to what the best way of identofying the threat, then laying the guns on it would be - there are various options.