"unfortunately, the update has to be manually installed via a USB stick plugged into the car"
Why is this unfortunate? that's the way updates to a car SW should be done! Only by physical access, that keeps things safer.
I guess you could give the car some kind of wireless communication, so it can download the update automatically from the internet, but that connection might become a source for malicious attacks...
wait, WHAT?
Biting the hand that feeds IT
