Mageia 6 supports over 25 desktop environments and window managers.
You can load them all, and then go from one to another.
​Being able to load multiple desktops onto a single system isn't the issue. I can do that under Mint.
So I'm not interested in the theoretical "you can do this". I would like to find out if anyone has actually tried swapping KDE to/from GNOME and whether it worked or not.