@murgero thanks for your suggestion, we have thought of creating folders for each user with symlinks to the accessible app data directories. Can you explain a bit further what you mean with the virtual directory support in SFTP servers? We currently use proftpd with app data directory be handled over as an LDAP attribute and set as the root dir for the sftp connection.
Jasmin - Open source SMS gateway
Cloudron 3.6 - new plans