This seems like it could be pretty easily solved by an actuary...the only political question should be "how much risk is too much". Obviously, we're more likely to keel over as we get older, as, IMS, no one gets out alive. And the information couldn't be more accessible. Get some statisticians on it, present the findings, and have an earnest, public conversation on the statistical likelihood of "death behind the yoke" (vs., say, the statistical likelihood of youthful indiscretion or pulling through the pusher and crashing the airplane) Of course that will never happen, because, like most "Safety" arguments, it's not really about Safety at all...at least not the Safety of the passengers.
Personally, I suspect that the benefits of having highly experienced pilots up front far outweigh the possibility that they might meet St. Peter at any given moment, but that's a suspicion, and why trade on that when we have reams and reams of data?