Back in SWG, there used to be city battles, where either imps or rebs would be attacking/defending a city, such as Bestine. It was really fun because it existed on several worlds, and the times would be staggard every several hours. There were NPC forces on each side (+ vehicles), including a "General" boss type unit for the defender. Different classes have different ways to contribute to the effort -- PVP battle, slicing, crafting/building, etc.
We had some great, great battles on those invasions! If I were a producer for SWTOR, I might give it some good consideration!