I'd like to make a comment in reference to the thick door on the loading platform. We often say there is a prototype for everything. A thick door like this could actually be two doors.
As boy I would ride my bike to school and right by the local Purina feed mill here in Orlando. I remember seeing the two doors on the platform as I would stop and talk to the workers mainly so I could be close to the boxcars and see the Seaboard RS-3 switcher as it pushed the boxcar in place by the loading dock.
Anyway, the outer door was solid wood and rolled on heavy rollers attached to the top of the door. The inner door was solid as well but had an opening as seen on this model. The inner door had screen in the opening so the door could be closed to keep the birds out of the warehouse and still get ventilation. The outer door closed over the inner door.
The thick door is no big deal!