I've considered submerging the rings in thinned resin and pulling a vacuum on them, but haven't tried it yet. I didn't know if that would incorporate the resin enough throughout the wood to improve its strength. It's definitely worth a try though. I may also try coating them in UV resin instead of CA glue to see what effect that has. There are some "nano" ceramic coatings used in the auto industry that could give them some extra scratch resistance too.
The major downside to the resin coatings would be significant wait times for curing, and a whole lot of messy cleanup. If it works well it could be worth it though.