It's been pondered upon, but i think the limiting factor is the fact you must maintain a network connection, which can be tricky in the car. Also, what are you gaining by going this route? One of the primary benefits of a tablet is that its either always on or very quick to boot. In your setup, you're still going to be dependent on a PC booting/resuming.
I guess it would be ok assuming you're not planning to do anything mission critical (does your tablet come with GPS?)