You're not the only one with this idea. It has been brought up on multiple occasions in the past. However, there are a few problems with the proposal:
Call of Duty is based around close quarter combat; nonstop action, which is part of
Call of Duty's popularity. If Call of Duty were to expand the maps to the size of Battlefield 3's, the action would diminish and gameplay would slow down.
Now before you say "then add vehicles", think about it. Vehicles are what separate Battlefield and Call of Duty. If vehicles were added to Call of Duty then it would be very similar to Battlefield but with a different titles. Both games aspire to be unique. It's the reason people buy games.
Also, larger maps mean more graphical details. More graphical details mean less FPS, which is the wrong direction the developers want to go. They want to keep a buttery, smooth 60FPS.
If Call of Duty ever happens to use Battlefield sized maps, don't expect it until the next generation of consoles are released. Until then, you will have to play Battlefield if you wish to play on larger maps than what Call of Duty currently offers.
I'd like to see a range of map sizes, from small, frenetic maps to large, slower style gameplay.
My issue with Battlefield was... yes the maps are huge. So I spent most of my time running just to get into the action(if nobody in my squad was in an area where I could spawn on them). If I wanted a running game, I would buy a running game. I want a game where I can quickly get into an engagement, and thats always what CoD has offered. In fact on some of the larger maps, I find myself running around trying to find the action. It seems to me that the best CoD maps are usually the small to medium sized maps, big enough where you are not spawning on top of one another, but small enough where the action is never that far away.
I personally loved the maps on Black Ops and hope they stick to that formula, with more innovations and improvements of course. They had multiple routes, good combos of CQB and long range engagements, and I had a lot of epic battles on them.
No I wouldn't. I like both Battlefield and Call of Duty and I expect a different experience when I play these games. CoD doesn't need big maps and vehicles and I don't think it ever will. I like CoD's medium sized maps and it makes for fast paced gameplay which I like. They're 2 different games and it should stay that way. BF3 tried to compete with CoD a bit in its campaign mode CoD doesn't need to compete in its multiplayer its already out on top
Look, its never going to happen, If you want large maps go play BF, Cod is a close quarter arcade FPS and always will be, its fast like its always been, Like the saying, "if it ain't broke dont fix it" And they will never change it cause thats what everyone loves cod for the fast feeling and short games, not everyone wants to be stuck on one map for around 20 mins as it gets boring after a while..