Just something I thought of. On Windows, there's this little feature called a
Virtual Hard Disk. Which is.... a disk image. You can mount it, and it works pretty much the same as a physical mounted drive.
They
are usable with cloud storage. Some people use it as an
additional layer of encryption.
Which makes me wonder: What would happen if you put a copy of Calibre Portable and a library on a virtual hard drive and then put the VHD itself onto the cloud storage?
Since the cloud is only handling the container file, while Windows itself handles the files inside....it should work to prevent most of the issues that come up with Calibre in the cloud. If I'm right, it would even be a potential solution for Google Drive eating the ID numbers.
A few limitations: It can be a bit of a pain to set up in the first place. You could only have the VHD mounted on one system at a time, or the disk file itself would conflict. I'm not sure if Linux or Mac have VHD mounting (and even if it did, Calibre portable only runs on Windows).
I've only got one computer to test this with, though. Would anyone be willing to try it out and post the results?