In a similar vein, here's an XPK filesystem handler [1]. XPK provides a system for anyone to write their own compression/decompression libraries. Anything that uses XPK will handle whichever compression format you have an XPK library for, entirely transparently (many applications have application level support for XPK too, but the filesystem handler is much more generic)
This resonated with me somehow, despite never using AmigaOS... And then I realized TotalCommander can also treat archives as folders (aside from solid RARs, I suppose).
While that is true, that was an application-level implementation.
With an OS-level file-system implementation, I could in any application just double-click a ZIP file, open a GIF or JPG inside it, make my changes and save back and the ZIP was now updated.
It was one of those small things which made a huge difference in the user-experience.
You would just cd into the file and the rest was magic. I've always missed that feature since moving to the PC.
In lots of ways, AmigaOS was way ahead of its time.