My car for example doesn't have reliable connection when it's parked in the garage, which is where I charge it.

Your solution would add a lot of extra edge cases that needs to be considered.

You have to ensure the updated key is reliably transferred to the mothership in a timely fashion, and subsequently that the key is reliably transferred to the car in a timely fashion.

That's the back-end stuff. There's also the front-end stuff, like will my SO understand why her app isn't showing the car's location but mine is?

Not saying it's impossible, but it adds a lot of complexity beyond simply encrypting the location with multiple keys.