I added a second level/mezzanine level to my model, which also meant I added a staircase. I worked with paper at a 1:20 scale. I definitely prefer working with cardboard as it is more sturdy, though want to save that material for a later more detailed model.
Some of the details I didn't think out properly and meant that there were gaps in the paper. I also wasn't sure If I should somehow make one large window across both the top and bottom level, or leave it as two seperate windows.
I also made my Fusion360 transitional space model out of paper.