Earlier I’ve used Knox from Agilebits to open encrypted vaults that contain DEVONthink databases for sensitive information. The vaults are stored on disc as sparse image file. It’s a bit of hassle to open first the encrypted vault and then open the database in DEVONthink, so I was intrigued to try the encrypted database option in DEVONthink 3. However, despite its extension .dtSparse, it stored the database as a “block” image. It’s an issue when working with a database of this kind at least when it comes to backups, which I have in Time Machine, Arq and on an USB disk. They’ll need to backup the block file each time a single change is made in a file.
I tried this feature and it made it more convenient to create encrypted databases this way. However, I don’t know if I want to use them because of the block limitation. Are you planning to support sparse kind of images in future?