> Steel frame, flame retardant insulation and cladding, rammed earth, .. these are all options.

Don't even have to go that far.

Wood framing is fine: make your cladding stucco would do a lot (or brick). You can even have siding as cement-base stuff is available:

* https://www.jameshardie.com/blog/siding-types/what-is-fiber-...

You could have metal or clay roofing, but shingles with a Class A rating is available as well:

* https://www.ameriproroofing.com/blog/asphalt-roofing-shingle...