I understand this is not a suggestion forum and that BIS may not have the manpower to pull this off, but it is something to bear in mind should they ever have the assets to make this My idea is making improvements to the driving model for ground vehicles, just like BIS improved the helicopter flight model. Also be advised that I'm also making a suggestion for the control set-up below, plus a few details on how to do certain things in the model idea, though they may not be the actual part of the default set-up should this be added.

Controls:
Accelerate/Reverse: W
Steering left/right: Mouse/A, D
Brake: S
Enable/Disable handbrake: X
Seatbelt on/off LCtrl + X
Clutch: LShift
Gear shift: LShift + Mouse
Gear reverse: LShift + MMB

Startup process for manual gear:
Players will have to hold LShift (clutch key) while scrolling to start up the engine. they will then have to put the vehicle in first gear using the mouse and release the handbrake by pressing X. Then they will have to hold down W to accelerate until the vehicle starts moving forward and release LShift. Failing to do so will make the engine stop.

Startup process for automatic gear:
Turn the engine on, hold LShift and put the vehicle in Drive, then press X to release the handbrake and hold W to accelerate.

Switching gear for manual gear:
When the engine starts over-working itself, players have to release W, hold down LShift and change gear, then release LShift and hold W to accelerate. If the player fails to do so and the engine will choke.

Reversing:
To reverse, players have to bring the car to a full stop, then hold down LShift while pressing MMB. They can then press W to reverse the vehicle.

Parking:
To park the vehicle players have to bring it to a full stop, then press X to enable the handbrake and LShift to put the vehicle in free/park and turn the engine off.