He did have a good idea for a police one. Is your NSX UV'd (and will there be a police one with atleast a lightbar)?
Theirs a dedicated thread to suggestions, Link: https://www.beamng.com/threads/vehicle-suggestions-see-first-post.79/
Yes and No, for all I can tell, it started in 2012 meaning yes the devs make them. At the same time, some suggestions are never made due to reasons. And not just cars but features also. Just don't spam request or start a flame war.