AmigaOS actually did use : as a volume marker and / as a path separator below the volume level. "Volumes" on AmigaOS were actually more like generally-usable filesystem namespaces; the feature covered not just "hardware" volumes like DF0: or DH0: (equivalent to A: or C: in MS-DOS) but "logical" ones as well, which worked a bit like chroots in a modern OS.
You could even use a physical medium label as a volume, and the OS would interactively request (via a dialog box) that the user insert the requested media into any physical drive, so that the system could interact with it; the whole notion of "is this media/physical resource available right now" was something that the OS would abstract away for you! (I think the closest thing to this currently might be RedoxOS's idea of using URLs as generally-applicable path indicators, since URLs too have a base-level resource indicator (the "host" part) and a subpath.)
Program options were dealt with by requiring paths to be entered as strings in quotes in the general case, and disambiguating them only as a last resort. There was no option prefix at all, so you would enter, e.g. `list files` as the equivalent to `ls -l`, and `list "files"` to list only something named "files".
You could even use a physical medium label as a volume, and the OS would interactively request (via a dialog box) that the user insert the requested media into any physical drive, so that the system could interact with it; the whole notion of "is this media/physical resource available right now" was something that the OS would abstract away for you! (I think the closest thing to this currently might be RedoxOS's idea of using URLs as generally-applicable path indicators, since URLs too have a base-level resource indicator (the "host" part) and a subpath.)
Program options were dealt with by requiring paths to be entered as strings in quotes in the general case, and disambiguating them only as a last resort. There was no option prefix at all, so you would enter, e.g. `list files` as the equivalent to `ls -l`, and `list "files"` to list only something named "files".