I would really like to see some better options, and I could see it being farther reaching than just a bass stool as a lightweight and easily portable stool that is also comfortable and sturdy seems like it would have tons of potential applications. The drawback is that height, or height adjustment is far more important to us as bass players than soccer moms, campers, picnic attendees etc.
+1 on all counts. Making it adjustable always adds weight and reduces stability. I might try my hand at this. First, the seat itself I think must be a rigid piece, not cloth. Perhaps it could be hinged so it could fold in two. Second, I might just make it in two or three fixed lengths rather than adjustable. An obstacle for me would be selling to North America. My Capos are easy enough to direct mail from Europe, but a stool would be to big. I'd need to find a reseller. So, I've got the bug, but this will take awhile. Don't expect to get one anytime soon. If this were done properly, it could conceivably fit into a bow pocket on your bag!