geo wrote:
You can spend less than that on a basic version just using rebar, concrete &
the airform and it would be much stronger. Or you can go whole hog with the
insulated version with electronic sliding door, etc. It's a very flexible
system.

Foam concrete (or concrete foam)?
Come to think of it, one could use the construction methods used by
college Civil Engineering departments to fabricate concrete canoes and
entrained air to create a lightweight structure.
The airform would provide the support for the couple layers, then spray
on the successive layers.
That would be an interesting college challenge problem.
Materials could be donated, the military would provide research grants.
Forget the college challenge, I'll just apply for the grant!