Just I have tested compatibility of Google Drive and Calibre - found it works (now). Maybe I do not quite understand the whole issue or Google has changed something.
I uploaded individual files (single books) or entire folders (e.g. total author collections) to Drive, then deleted these on my laptop (not just from caliber away) and downloaded them from Drive back. The files/folders come .zip compressed and you have to unpack them.
This all works very quickly an easily, after adding to caliber you may read, edit book and metadata etc. as usual.
Please check by yourself and possibly edit the
Warning sticky post.