Okay so i found vehicles to be less complex than I feel it should be, now I dont ask that it gets over complicated but i think this idea might appeal greatly.
Vehicles should have gears, not quite complicated in the sense that you would require all available gears and the use of a clutch to switch. but somewhat complex and simple enough to actually be useful
currently, vehicle has something of a normal speed and a turbo speed, and that is it.
So what I suggest is to use the Q and E buttons for gear up and gear down. Lowest gear obviously gets you into reverse, first gear to get you going to pull away, this would get you to up to about 20km/h. second gear to get you going going at normal speed up to 40km/h, and 3rd gear to cruise 80km/h, (think fuel saving)
But here is where it really counts, lower gears can be better used for climbing steep hills faster and easier. and go off road with more control over speed. Normal speed being capped at 40km/h will make navigating towns much easier without having to tap tap tap to accelerate through twists and turns. Higher gear will get you to travel on roads at greater speeds and be more fuel efficient (not that I think it matters that much)
And then there is still the turbo feature, basically this can play a good role with these gears. So for example, while all gears are capped at speed limits, Turbo essentially over rides these caps, meaning you peddle to the metal. So yeah in lower gear you can climb hills easily, adding turbo will boost power and get you climbing faster up to 40km, but do it downhill or on a straight, and you risk blowing your engine. With normal speed you can go from 40km/h to 80km/h (as an example) which is perhaps great when you need to move quickly out of town. and high gear will probably get you to 100 maybe 120km/h just cruising, how ever Turbo too early or try pull away faster in a high gear and you will stall the vehicle.
I believe this can make vehicles much more interesting and effective.