[z3t4]

When all other layers are secure, like wearing a bulletproof west inside a bulletproof car inside a bunker that can withstand a nuclear blast. And add to that some security by obscurity, like a bunker in a secret location, only accessed via a tunnel.

[z3t4]

That said, if security is top priority you also want to be ready if you get shot from within the car. But more importantly you need to define the most common scenarios and make sure you are protected from all of them. One scenario might be someone shooting you, but another scenario might be food poisoning which would require an additional, different solution.