I did it this way : Idea for quick switch bed: feedback requested
It’s a bit overkill, and not perfect, but mostly works.
The added baseplate is milled flat so all inaccuracies related to the build plate are gone. And the other ones are easy to replace and are flat by design.
You lose some height, and it adds some weight, but you gain a lot of comfort. With the print bed it is not perfect as the mdf does start to deform after some time. Especially for higher Temps. It’s pretty stable if you don’t go over 50degrees.
Humidity might have an impact as well. I have been on the lookout for another material for the printbed.