I think the medical tourism industry is underdeveloped. One can get major surgeries like joint replacements, cancer treatments, or heart jobs done by quality healthcare providers in a lot of countries for six figure discounts, even at their retail prices. That option isn't much help in the ER when you don't have time to preplan, but having such an option certainly reduces the need for insurance. E.g. one might accept a policy with a $750k cap and then be able to drop $50k on medical tourism if needed while still having sufficient savings to stay retired afterwards. This would cover all contingencies except an emergency with costs exceeding the max - which probably doesn't occur as often as we might think due to the saliency bias.
Besides, these massive bills are usually incurred during a person's last six months of life anyway. Are we working an extra 5 years of our physical prime to ensure we get the treatment to suffer through those 6 months? That's not a hypothetical. My grandfather-in-law opted to go through bypass surgery in his 80s. This was followed by six months of a terribly painful institutional existence followed by death. Good thing he had coverage for the half-million dollar surgery, we might say, but in hindsight that coverage allowed him to make a choice that turned his last 6 months into a living hell while churning up a huge bill. He would have been much better off dying at home from the coming heart attack a few sweet months after declining the surgery. Perhaps being truly FI means having the courage to accept death when it is time, instead of burning away our healthy years working to earn end of life care.
My third thought will be controversial, and stands independently from the first two, so feel free to disagree. Perhaps at some point of cancer, dementia, organ failure, pain, etc. suicide or assisted suicide is more rational than the way things currently work. As a family member of multiple people who suffered through end of life care, I can attest that I gained nothing from their heroic suffering, and instead experienced my own pain and worry watching them suffer. Perhaps a better life would involve a goodbye party, a time capsule, some songs, some cake, a review of old photos, a few interviews for posterity, and then you take the injection. This seems far more dignified than a couple of years of nursing homes or losing one's self to Alzheimers. As a side bonus, some inheritance might remain intact, potentially allowing the next generation to live more fully instead of running on their own work/healthcare treadmill. Life would end in an event of love, giving, sharing, and hopefulness for the future, instead of months of bedsores, pain, and mental deterioration. This will seem sick and twisted to some people, but it's the culture I'd rather live in.
Remember, the definition of risk is: the probability of not achieving one's goals. That excludes a lot of what we worry about.