One can easily use 1x1 square tubing and 18 ga sheet steel and make a door for a scoolie. Just cut the tubing and weld the sheet steel to it. Hinges can either be the piano hinge from the existing bus, or steel door hinges for houses, or even from the hardware store.
A window with safety glass in a rubber frame should be used and low enough to see traffic, esp if you drive in the fast lane like i do. If you notice, semi's even have a small window at bottom front of pass door (usually blocked, but shouldn't be). You can frame in the window with box tubing for strength if you do it right.
I have built doors for all my previous busses. Yesterday, I got out some tubing, and steel, and angle with the holes in it, to build a two piece door. The bottom door i believe is 32x53 1/2, which will be the generator door, and go a bit in height above the 10 inch raised living room floor, and i haven't measured the top for a door with a window yet, but it will be something like 32x 36 or so. I have been scrounging around on my property, and my neighbors machine shop acerage, to find a 24x24 or better window from a rig or rv that has safety glass. Think there is one about that size on a monico rv at his place...
Of course i will only be able to insulate them the depth of the doors...
Nice pictures of the RV door instillation.