Some useful links:
sanded on here sells flax cloth through his business, you could DM him to buy material and get insights.
Worth following them on Insta and going back through their posts, there’s a lot of flax and other alternative materials in there for inspiration:
Never used, it but have been getting alternative boards built for 20+ years.
Shapers/glassers are willing to build most anything if you pay them. Find a local shaper willing to do contract glassing and provide the materials. That’s the easiest/quickest way to vet a material you’re interested in trying. Build it and ride it for yourself.
Something else to look at if you’re interested in durability/performance/lightness is cork. Go follow this guy on Insta:
Been riding his boards for 15+ years. He’s doing carbon/cork/vacuum bagging
BTW, this post looks like it’s in Board Archive → Materials category. You’ll get a lot more views/feedback if you repost it in the General Discussion category.