If you absolutely must access the library through calibre (and do maintenance) on multiple computers, you should use some sort of File Sync software, e.g. MS SyncToy.
Mirror the library onto the NAS, and make sure everyone updates their copy from the mirror before running calibre, and updates the mirror from their copy after they close calibre.
Do not have multiple people accessing calibre at the same time!
database clashes.
The same principle applies to Dropbox/OneDrive/Box/Copy.com as well.
...
Much simple and less hassle to use the Content Server for remote access/download.