I'd like to see more inventive maps. Personally, I don't care if the maps make any sense. For example, i'd like to see a MP map on the moon. With a decent sized outside area where you could moon jump and what not. Give me a map with a small warehouse on the docks with a docked cargo ship (Put two zip lines on the roof of the warehouse that take you to the front and back of the ship, giving you more ways to get on it.). Give me a map like MW2 favela where I can have some rooftop gunplay. Give me some serious vertical gameplay.
I've always liked the idea of adding older CoD maps to the rotation. I liked the MW3 idea of giving them for free much better though.