Motion-locked z-doors for vehicles.

I would like to propose being able to enter a vehicle while it is placed, allowing you to build certain things inside of it. This would allow you to customize the inside of a vehicle and make it feel more personalized, making vehicles less of "just another mode of transportation", and more of a mobile miniature home. This would only apply to vehicles of appropiate size though, as "entering" something such as a bicycle or a small car would be a bit weird. Anyway, that's my two cents into vehicles.
 
Top