Having a variety of vehicles in Arma 3 will make gameplay even better! In Arma 2 the government vehicles were only police car and ambulance(as I'm aware of)Here is a list of vehicle I'd love to be in the game. (these are mainly government vehicles)

Police Car - Working siren and lights

Fire Engine - Working siren and lights

Ambulance - Working siren and lights

Police Helicopter - With working spotlight (maybe passenger can control it)

Medic helicopter - When injured is on stretcher, stretcher can be placed inside and then transported.

Tow truck - Can tow cars

Aircraft transporter (thingy) - Can attach to aircraft (like tow truck) and move them.

Chinook - (Used in Arma 2) - Can load up to certain amount of troops or 1 vehicle and half amount of troops or 2 vehicles(Just example)

Limo