Yes, a full scale Guitarde would be great, unfortunately such opportunities are rare today it seems.
I also believe that building it full scale would be a different kettle of fish, so to speak. I think of larger timbers and the joinery.
Nevertheless great work from Adam, especially because I do not believe there are many carpenters who are capable to do this kind of work. Model or full scale.
I was a little surprised he used the Billon book as a source. I considered it rather poor and sold it a while back. He did well to decipher that book's section on guitardes.