Yes, it's perfectly possible to write Archimedes disks back to floppy on a PC using a DOS program called 'Arcimage' available from http://knowbody.org.uk/arcimage/
I suggest you grab both versions 1.1 and 1.2
Version 1.2 adds support for 1600k floppies, but support for 800k floppies may be broken. However, 800k floppies are fully supported in version 1.1
An intermediate version 1.1.2 is available from http://bbc.nvg.org/software.php3
in case you find other bugs.
Development of this utility is rather patchy, being the result of three programmers' effort - each working independently. Details are provided in the readme files.
For completeness, the original version 1.0 (executable only) is available from http://bbc.nvg.org/util/Arcimg.exe
A combination of these versions of this utility will certainly fulfil all your Archimedes disk imaging/restoring requirements.
Hope this helps!