I think it would be nice to have a VFS (commons-vfs) based FileSystem which then can be used by BundleFsPersistenceManager.
For example, I have worked with a Jackrabbit based WCMS product which recommends using one of BundleDbPersistenceManager components for both workspaces and version, which makes it easier for clustering.
One typical problem is that the version storage in DBMS keeps increasing, so as a result we've recommended cleaning up older version items periodically. (You may google "cms version cleaner" for more info.)
In this case, if they were able to configure a VFS based FileSystem and the generic PersistenceManager, BundleFsPersistenceManager, for the versions, their DB size would keep small enough, and they may keep the version items almost infinitely. Actually versioning are used relatively less than other normal functionalities such as content retrieval and searching, only when authoring users publish a document in our case. So, keeping version data separately from database wouldn't be a problem, as long as it supports easier clustering (through WebDAV or SFTP in this option).
Another possible use case is that some people may use VFS based solution for both workspaces and version, backed by a clustered WebDAV server or SFTP server. They can use VFS-based DataStore provided by
JCR-3975 as well. This would increase architectural options around Jackrabbit ecosystem.