I am evaluating DT3 with my local NAS archive and its working really well.
I can index the archive and move the files into the database when I need them offline and move them back with any alterations.
If I am disconnected when I try to open an item in Devonthink that is on the NAS. It tells me its unavailable, however, has a mount button to automatically mount the archive using credentials in keychain.
I wonder if this could be extended to an auto mount and dismount feature, some sort of mount manager. Especially to auto dismount certain sources when I close Devonthink and connect on start or when a database is opened.