There are a lot of things that need to be changed in order to make the game perfect. However, most of these fixes are not something that are going to be included in any of the DLC's. What I really like to see is really good symmetric maps, like in Gears of War. Both sides should have places for snipers, undergrounds for shotguns and open area's for AR and LMG's. Of course it should include a good Zombie map as well.
Extra DLC that include zombie maps like Moon, Kino der Toten, Nacht der Untoten would also be nice. Something they could put-up for like 600MSP.
I like the idea of them adding in guns. I'd like to see an assault rifle from a past CoD game make its way to the game - particularly the M16 as it's been my favourite weapon throughout Cod4/Mw2/Black Ops 1. The Spaz-12 would also be great to see since there's little variety when it comes to shotguns; only the first one is good, the rest are meh. I can see them putting in a new sniper rifle to try and sell the DLC to all the fanboys out there though :/