An example of something I've thought about for, oh, years, and in 5 minutes had a successful proof-of-concept test of: scale shingles (HO in my case).
Actually easy to make, although a bit mind-numbing. I have a whole bunch of scraps of pressure-sensitive label material, left over from my previous lifetime as a printer. (AKA "crack-n-peel": you know, the peel-apart sticky label stuff.) I scribed some parallel lines for the courses, made marks every scale 6", then made two very close cuts at each mark. Was able to pretty easily remove the resulting thin sliver at each mark, making the space between shingles.
It's like making your own storebought shingle material: after that it's just cut, peel, and stick down. The small sample I painted (gray primer) looks good. My next paper model will be covered with them. It's going to take hours and hours of cutting, which I'm not looking forward to, but I think it'll be worth it.