There are 70 year-olds who are sharper than 25 year-olds. On the other hand, there are many staying well past their prime.
It reminds me of what some states are doing with driver licenses. After 65, they make the renewal interval tighter and make them come in for eye exams.
While tightening up the interval for physicals isn't applicable here, maybe there's something else that could be done.
We all know that there are flight docs who are known to give easy passes. Perhaps the FAA could certify a smaller number of select examiners as "geriatric aviation medicine" specialists, and require them to certify older pilots as not falling prey to the maladies that accompany aging.
I know it won't happen, but I think it would answer the mail.