So, thought I would follow up on my post from a while back. The watch repair expert who identified the problem for me here in Hong Kong successfully replaced the bezel ring with a newly made replacement (courtesy of another guy who does this stuff in HK) and kept the DNN insert that came with the watch. For those who wondered how the bezel ring was staying together at all, the answer was glue -- probably UV glue, which was also keeping the insert attached to the bezel ring.
So this means I can now enjoy the watch without fear of the bezel falling off (or pieces thereof), and if I come across a decent DON then I always have the option to swap it in.