Hmm... there are already Constitutional requirements, so that even if voters favored such, they cannot elect a non-citizen or someone under the age of 35 or who hasn't lived here at least 14 years. So it is NOT wholly the choice of the voters. It is the voter's choice among qualified candidates. And look at the mess with Colorado and Maine trying to throw Trump off the ticket. The Constitution clearly gives the states the authority to conduct general elections and there is a good chance that decision will be reversed by a later court.
Closer to home I would favor mandatory, annual skill testing for drivers over, say, 65 - even though I would be subject to them myself. I do not want to authorize ageism in any field, but it is ridiculous to pretend that humans do not begin to deteriorate both physically and mentally as we age. Airline pilots are required by the FAA to retire at 65. Other federal positions that have mandatory retirement ages include firefighters, nuclear materials couriers, air traffic controllers, and customs and border protection officers. (
Yes, employers can set a mandatory retirement age. What you need to know. It could hardly be argued that age deterioration in the presidency does not threaten as much public harm as it does for those individuals.