It would be nice if you drive with a lightbar (like amber or police lights) that it also comes with a small control panel/indicator on the dashboard. This control panel should then also have a light on it that indicates when your lightbar/police lights are on. This way you don't have to go in 3rd person mode to see if your lightbar is on, you can just look at the control panel. For instance, maybe do like a blue flashing light indicating when the lightbar is on, and also a red one indicating that the siren is on.
In addition, maybe it would be nice if more lights were flashing on EMS/police vehicles. Take the Bastion police car for example. When the police lights are turned on, headlights also flash, so do the reverse lights. Very nice. This could also be done to other modern police cars like the ETK K series polizei or the Bastion unmarked police car.