There is little point adding this to the regular Skoda police cars used by TruckersMP Game Moderators and above. Not only is it an entirely valid point about players wanting it for pilot cars, but Game Moderators effectively never need to close roads on the normal servers.
During Real Operations, where there are members of staff blocking roads / parked at incidents where this may be useful, it is more likely that staff would have different vehicles to the normal police car anyway, the Skoda is surprisingly used very little during Real Ops! A sign on a Real Ops vehicle might be nice, but on the regular police car, not sure it's neede.d