I believe sense when you get in a vehicle and you automatically hear the engine turn on or when you on a traffic stop and you need to turn it off there should be a way to do that, I believe the following features should be added.
Engine on and off GUI switch
Hazards have a sound to them.
These will improve RP and the users experience to the max, adding more realism and much more!
(Now see it would be more laggy, can’t wait for new car features tho!)