Custom Vehicle Traffic

So, I'd like to customize what goes into traffic.

More specifically, I want to spawn in one of my configurations (turbocharged Moonhawk Police Car) as a cop.

Is this feature in the game, or is it planned?

 

Not sure about the police part but you can change the traffic, just spawn the cars you want the AI to drive and then switch to the car you want to drive and then click start traffic in the traffic menu

 

Thanks! It works with all official police cars too.
It worked on a modded police car once, but I think it was probably just a bug.