I've never had logging in with a different desktop environment cause problems. (And I wouldn't expect to. The desktop session selector on the login screen is there for a reason, after all.) Your comment makes me wonder what desktops you tried that stepped on each other, and what bugs you're referring to.
In any case, if I had an experience like what you describe, I would simply re-create my user account and its home directory. Going through a whole OS install as you suggest would burn a lot more time with no advantage, which doesn't seem "better" to me. To each their own, I guess.
Remember as well that your "distro spin" approach is only possible if such a spin exists. Example: If someone wants Linux Mint for its beginner-friendly community support, but also wants to try KDE Plasma, they can. But they're going to have to install Plasma after the base OS, and switch.