Can you make it so certain parts don't stop bullets, and let them pass through and hit the passengers?
Also, could you make the engine compartment more vulnerable to damage, perhaps the way you make different parts of a tank take different damage?
If you did both of these, and made the vehicle take 1/4 the damage from collisions it does right now, you could set the engine to fail at 75% health, and make side panels take very little damage from bullets, but let them pass through, you would have a very realistic vehicle.