When there is some vehicle on the terrain, you can click it double time to open it atributes, and change vehicle type, or simply delete it. Problem is, of this crew is allways staying in this vehicle place (inside of it, so you cannot see it). Its very problematic if you change 3 crew vehicle to 2 , and one of crewman will be "inside" vehicle and commanding it. Problem appear to modded content as well - for example in RHS, if i spawn T-90A and change it to T-90, the crew (3 man) stays "inside" vehicle, after mission start they just walk from the vehicle.