An appealing idea. I would also consider such an insurance.

I also see a problem, similar to kilobug's second point: How would such an insurance handle a person refusing some recommended treatment? Especially if the treatment is effective (say in terms of life expectancy), but also has nasty side effects (for a while/for the rest of your life/etc). The parallell obvious to me is life insurance and suicide, but life insurance does not pay out for death due to suicide. The policy becoming void if treatment is refused (without caveats) would, however, be a dealbreaker for many people (me included). As far as I can tell, Robin Hanson's proposal also does not address this.

I can imagine wanting to say something about what risk/quality of life/life expectancy tradeoffs I would want to make (and thus what treatment I would refuse), but it's not clear to me how something like this could be specified.