Your handicap argument has nothing to do with age discrimination in employment in which you're conflating extant disability with risk of disability (or you mean something else entirely by "employers can do the math", feel free to elaborate). Sure, disability management is a problem, but it's a *different* problem to excluding people over 50 for employment they're otherwise qualified for, based on the fact that they're more likely to become disabled than a 25 year old (younger than that there's some pretty horrible accident rates due to their inability to assess risk).
BTW, I'm not suggesting re-skilling in "hot" professions against a tide of experienced people, that's a straw man. I'm suggesting finding employment in a different field that is viable with reduced physical ability.
It seems like you're arguing a personal situation against the general case, and that is not the question at hand. If you want to argue that society/government need to do more for the disabled, then you won't get any argument from me, but to posit that it's OK for business to manage their personal corporate risk at the expense of society, I won't accept that at all. Alternatively we could go all Logans Run and solve both problems, but I don't think we're there yet.