They could add a new gamemode called "Convoy." It's in the name. Basically one team has to protect a Convoy and get to the end of the level without losing all their vehicles, and the other team is trying to destroy them. That would be a lot of fun.

Convoy order: Tank in front, 2 - 3 troop trucks in the middle, then a jeep or another tank in the back. So troop trucks would allow you to respawn next to the convoy. If you loose those trucks you lose the ability to respawn, but the tank would be able to shoot and defend them rather effectively so destroying the tank first would be a priority. Obviously the only thing that could destroy the tank is a rocket launcher or some well placed TNT. So it wouldn't be too easy to destroy the targets since only two players in the whole team can actually destroy objectives. Air support should be disabled as it would be OP. Also along the way maybe you'd have obstructions in the road that you'd have to clear out of the way to allow the convoy to move.

If a vehicle is destroyed in front of another vehicle, the whole convoy must stop for 3 seconds, and then it will begin trying to drive around the obstacle.