Great idea. I may be trying to make something with it. Don't have much call for jewelry but I like playing with composites and this is really cool for something decorative.
Have you considered vacuum infusing epoxy for those rings? If you infuse epoxy into the partially completed blanks (once you have cut it and exposed more of the wood) that may be enough to give it the strength required to complete the turning. This technique is often used for infusing epoxy stabilizer for pen blanks.
Simple vacuum chamber design out of PVC:http://www.joewoodworker.com/veneering/vacuum-infusing-chamber.htm