The problem isn't the qualified beds but the personnel. In contrast to gas turbines, which are small standalone plants where an operator already there essentially just presses the power button.
I don't think this would work here though, since enlisting to work in a covid ward is a hard sell when you're not being drafted, and standard of care would suffer with all the inexperience.
Substantially raising nursing pay and increasing the powers of nurse practitioners would be a good idea though.
Many people would happily do some courses (and plenty of refreshers) to be a stand-by nurse or doctor who only gets activated for a few weeks every few years, if they get a few tens of thousands of dollars for that trouble.