Well, EB I does kinda have this feature already. When you take over a city, you can choose to loot it, giving yourself lots of cash from the inhabitants. You can also destroy buildings for cash. You then retreat your army, letting the city fall back into enemy hands.

As for the little villages and towns not represented on the map that your army might raid, these are represented by the destruction (rough, black texture) to the map tiles should your army stay in place for a while.

What I would like to see is some understanding by the AI in terms of the units it spawns when cities rebel, so it can determine whether you raided the city and left it intentionally for the populace to reform themselves, or if you were careless about keeping the populace in order and they rose up. The latter would be where the huge armies of slaves would be suitable, whereas raiding in EBI produces these as well, which is rather annoying.