I wouldn't expect they'd ship that standard freight as it's a pressure vessel, i.e, Dangerous Cargo.
In my opinion, you really still need to run a hand held or two, there'd be nothing worse than coming across a burning vehicle and you can do nothing because your fire fighting equipement is permanently installed in your car, 10 ft away but useless.
In fact, in rallying, you still need hand helds even if your car has an installed system for just that reason.
And I couldn't justify the weight of dragging both types around.