Mm, people have been experimenting with paper/cardboard for quite a long time. Back in 1862, Antonio de Torres made a guitar with papier mâché back and sides, presumably to prove that the top was the most important component in sound production. We don't actually have any direct anecdotes from Torres himself about this guitar and his thoughts/motivations regarding it.
Belgian builder Walter Verreydt replicated the concept in one of his guitars some years ago.