1, 5, 8, 9.
There really should be skills to govern driving (both, car and motorcycles... and for flying too it ends up in the game). Such where the skill level determines how steady the steering is based on acceleration and driving speed and how reliable the breaks are. The faster you go/accelerate, the more skill you need to keep the vehicle in control. This would mean that superfast sports cars are for skilled drivers only - even acceleration might be a problem - while for less skilled, it'd be a pain and a health hazard to be behind the wheel (it'd not be fun and it'd be frustrating, but that's the point).
Outside the skill distorting the driving, I don't think it needs to be anything but "simple and fun", no overt racing game realism needed.
Cars should be hard to get. Very expensive and stealing shouldn't be nearly as simple and carefree as in GTA. No skillgates, though, everybody should be able to try out everything beyond their characters skill and see how it works.
Yeah, stealing should work both ways. If the player can steal cars from the NPC's, so should the NPC's from the PC.
Modding and pimping I don't care about. It's there or it's not, not a big deal.
But for misc gameplay spice, I would like to see a refueling requirement.