Back in ye olden times—back before MacOS X was a thing—the classic Macintosh operating system had a cool little feature called Extensions. These were, essentially, little TSRs—programs that ran and stayed running in the background. The obvious usage for these were things such as device drivers and custom theme systems, all of which can be accomplished on Linux just fine. So, why are Extensions so cool? It was all about how easy they were to manage.
An Extension is a single file that you simply drag into your Extensions folder, and the next time you reboot, the extension is loaded. (Those icons along the bottom of the Mac OS boot screen? Those are Extensions.) Don’t want to use an Extension anymore? Simply drag it out of that Extensions folder. Is one extension causing problems? Reboot holding down the Shift key, and all Extensions are disabled. Handy. Easy.