Yes, as an old (more years than I care to mention) Mac hand I have tried all the tricks you have mentioned.
My camera connects directly to my Mac through USB and authomatically opens iPhoto. I close iPhoto and launch iMovie and import directly into the programme without difficulty. When the clips are imported the Archive button should be available but it is not. I am now wondering if the glitch has something to do with the Sony camera not supporting this facility.
I would still be interested in any further thoughts you may have. Indeed, if you could lay your hands on a Sony digital camera have a go and let know if your are successful.
Of course, I can copy my files as an archive using a long way round but it would be nice to have the archiving facility as a valuable shortcut.