No no no - Drop the paintball part
That would just make the game seem too childish.
This is a war game, a spot of paint doesn't mean you're dead. Your body being riddled with bullets means you are dead.
Instead of having vehicles driving shooting at other vehicles, i was thinking more along the lines of a surprise attack on an enemy camp. Just a simple drive-in and slaughter type scenario.
Or maybe being put in control of a tank (just the one) - They could lock you in direct-control mode and actually let you go from area to area taking out the enemies, changing ammo for certain purposes, destroying buildings to get a better shot etc...
They did something similar to this in the most recent CoH game, sadly the tank still had a health bar, unlimited ammo, and always hit it's target. So it didn't do a great job of immersing the player.
In MoW it would work well though, you'd have to be careful to avoid AT guns/enemy tanks for fear of being destroyed instantly, or you might have your treads damaged and have to repair before you can move on.
Perhaps there could even be a scene when you must exit the tank to eliminate an enemy who could spot you and alert others.
Just thoughts though, as you say it'll be very hard to make and i don't expect to see it anytime in the near future. Maybe after a few more MoW sequels.