A good first step would be a constitutional amendment putting the Guard under absolute state control unless called into federal service by Congress (not the president).
As it is now, the president can remove the Guard from state control with the stroke of a pen. That’s another king-like power we don’t need.
If the Secretary of Defense decertifies National Guard units in noncompliant states with regard to the mandatory COVID vaccines, hen the units become entirely state funded and controlled. When Presidents Eisenhower and Kennedy federalized National Guard units in order to enforce integration against the will of the governors, that was in their role as Commander in Chief of the National Guard. However, they could not federalize the Arkansas, Alabama or Mississippi state police.
I hope the state governors don't blink and turn their respective National Guards become state militaries.