In a lot of (T)DM's that include vehicles you can jump into an enemies vehicle and just sit their are you wont be able to kill the enemies nor can they kill you. So, I had this though of when you just into the vehicle you can sit in another seat of the vehicle for around 2-3 seconds then the driver will be killed and you will be instantly switched to the driver seat.
I think its possible and will stop the problem people have with riding in enemy vehicles. I don't expect an animation of any kind and I don't know how this could be done if the vehicle is only 1 seat but if anyone could just get the basic function done that would be great.