Look at the MGS4 trailer again.
Instead of the frantic running around on a small map (i.e. Teamdeathmatch, Sneaking matches are better) you have teams systematically moving around a huge map while airstrikes are going on. You can move about in First Person View, which is deliberately made a little slower than Third Person so that the gameplay doesn't become a UT-like fragfest. This encourages you to use your head.
You and your buddy move out right, where Snake uses tactics to take out your buddy first. He lures you into a broken wall, and you don't call for help on the radio either because you are a noob, or because he used chaff to screw up transmissions. As you near the wall, he performs a swat turn ala Splinter Cell (or just runs to the other side when you aren't looking). Then he performs CQC on you, which is why the last thing you see is half a second on an angry old man lashing out for your neck. CQC is much more advanced in terms of animation and control (perhaps some God of War contextual presses can work here, or maybe they just give him a whole lot of animations to be randomly used.
Then Snake takes on the rest of the military convoy. Online you can control soldiers, metal gears and planes. Perhaps this "Sneaking Mission" will pit 2 vs many instead of 1 vs many, so that another person can use the little robot.
How does that sound?