To the best of my knowledge Google has no plans to fix this problem. I am not convinced that they think it *is* a problem.
That said, I have had some luck using Drive to "share" my library. The rules that work for me are:
- Only one computer can write to Drive using the Drive client
- Other computers can read (sync) from drive using the Drive client. They *must not* write files in the calibre library in Drive.
- Calibre does not access the library in Drive. Instead sync software is used from time to time to update the library in Drive
As you can see, following these rules make Drive useless for sharing a library across multiple computers for read/write even if calibre is run on only one computer at a time. They do permit CC and other cloud clients to see your library.
Also, I make no guarantee that the above actually works. All I can say is that using the above rules, during my CC testing Drive hasn't destroyed my library.