I'm not sure IW has they're weapons picked for DLC 2,3,4. A gun I would REALLY love to see come back would be the BAR, I know that would be out of the question as it's out dated. So why not the HCAR, the modern day variant of the bar. It can have have an integrated silencer (we need an LMG with a built in silencer it's annoying having to use the +attachment perk) it looks amazing, it would probably be the most mobile. I'm sure if IW wanted to do the two in one weapon style they are doing like with this DLC they could make it a marksmen rifle with some imagination. Take a look at this link and let me know what yout think. Then tell me what gun you would like to see and not something previously used by other COD titles.
Or they could add this weapon.
A smart weapon that takes the worry out of needing to aim. But then again if this weapon was in the game they could add windage and temp variances to the game too and it still would hit the target.
I'd like to see some love given to the less used weapon classes. A new shotgun or, preferably for me, a Marksman Rifle would be nice.
Any LMG will be the redheaded stepchild of the group anyway. Slow moving and low powered. None of them are the area control weapons they are designed to be in real life.