You have some interesting ideas here. There is a more fundamental problem. Mandating retirement at the age of 70 could be interpreted as age discrimination. Some justices have continued to be outstanding well beyond this age.

The other fundamental problems is that it is extremely hard to amend the US Constitution. It requires 2/3 of the House and Senate plus 3/4 of the states. Since the type of reforms that you describe would weaken the current power of lower population rural states, they would probably not support them

Significant leaders in both parties would have to admit the degree of failure in our system to accept change. I don't think we are there yet. In the meantime the "court packing" that has already been done by Republicans may block any coherent response to Covid-19, Climate Change, environmental destruction, and actual equality under the law.

It has often been argued that the Constitution is not a suicide pact. Unless we start it interpreting it and applying it differently then that is exactly what it will become.