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).
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.