While I like the idea, I can’t imagine it would pass a constitutional test. However, an age limit that kicks in only after a person has been in an elected position for X years probably could. This would allow an 81 year old that had never held office to run for the first time and not be discriminated based on age.

It won’t survive a court challenge, as the Supreme Court already ruled on this back in 1995 in the case of U.S. Term Limits, Inc. v. Thornton. The ruling says that states can’t add additional eligibility requirements to be elected to or otherwise serve in federal office beyond what the constitution lists.