You can normally type "end mission" if you get a mission that you don't like.
I can imagine that it is annoying to get killed while in car and then need to fight to get back into the car, don't know a simple solution though.
I can see both sides, but I'm going to go with no less damage or any advantages for the driver. The car does like what 18 damage on a direct hit or something? I don't want to see people pking in cars. Sorry, you need to learn to drive faster or find "cool" zones where the fighting is less intense.