Description:
In the same way the staff room limits the staff type that are permitted the vehicle depot should limit the vehicle types or at least give the option.
Why it should be implemented:
If you are building a row of a specific type of aircraft say commercial that require a specific fuel type you could limit the truck from using other depots that are further away meaning you should be able to refuel faster as the truck will always be closer, if you dont wish to specify leave all veichles permitted to enter, as the game progresses you may want to designate specific depots to specific truck types when there are more choices for example if a catering truck is implemented you may wish to build a depot near the kitchen (i hear this is the developers vision) and only designate catering trucks to it for a faster turn around).