A couple other things: it would have to be strong enough to withstand the weight of a car driving over it, and it would have to be waterproof (not to mention gas, oil and solvent proof) so it won't short out when you spill things on it.
There are light fixtures designed for installation in driveways or sidewalks, you'll see them sometimes in front of fancy hotels or places like that, but they're expensive and not easy to find.