@marcusquinn Interesting, generically what your saying is that instead of asking cloudron to expose an app's storage out to other clients we can have the storage an app is using be hosted somewhere else in the first place that would already be accessible to other clients and have the app map that external storage location into its own files system.
Looking at cloudron volumes it looks like volumes can be CIFS, EXT4, Filesystem, Filesystem (Mountpoint), NFS, SSHFS, and XFS and so any external storage offering including cloud hosted ones like Hetzner's Storage box that exposes its storage via CIFS, NFS, or SSHFS could be directly added as a volume which could then be mounted inside the application.
In the case of paperless-ngx I could create a CIFS share on a local windows file server, then add that as a volume, then map that volume inside the storage tab of the app.
I looks like one other wrinkle is that the storage tab of an app doesn't allow you to arbitrarily map a volume to any location you want in the app's file system but only map to /media/{volume name}
so you have to be able to reconfigure what path's an app is using for certain things to make use of an external volume or you have to move all of an app's data to an external volume.
Will test out reconfiguring paperless-ngx to point its consume directly at a mounted volume at /media/{volume name}
which should resolve our specific near term need for a features like this.