Yet another potential solution, if you're on Linux. This is more on the accessible side of things, it doesn't do separation as much as you would like it: KDE P

Yet another potential solution, if you're on Linux. This is more on the accessible side of things, it doesn't do separation as much as you would like it: KDE Plasma has what they call "Activities". In its basic idea, it's kind of like fancy desktop workspaces. So, it does separate your windows into workspace-like groups, but you can also set what files and widgets are displayed on the desktop on a per-Activity basis. So, you don't have a different filesystem, but you can have a folder or multiple folders displayed on each Activity's desktop. Also, shortcuts to different applications, including for example Firefox profiles, as well as different sets of widgets, for example I like to use the little post-it note widgets to write things down on. And yeah, with that you can then just switch between Activities via a simple keyboard shortcut or by clicking an Activity-selector on your panel (if you've put one there).