I didn't realize it would be this easy! I just went looking today if I could turn off mods to play a vanilla game of FO4 (still haven't got all my Achievements) and luckily this topic came up first when I started searching these forums. I had assumed "Purge" would have been, well, a real purge. Disable, nuke, delete, perhaps even see if the source file is available on the HD and delete it too. You know, a Purge. Not just a "Disable All".