It might be possible to use the content repository as the interface to IMAP folders and content.
I wouldn't think of this as a replacement for the way file storage does stuff (for large content clearly the way to go is to use the option to map content to the server's file system).
But it would provide a nice layer to write a webmail package on top of, and would make integrating IMAP content and non-IMAP content in a package a snap.
