With the new file system don't think there is a way to get items completely out of the DB ... even links to files in other repositories (local or remote) are recorded in the DB (meta data).
Was contracted to assist an entity migrate from a 2.3 system to the latest and greatest. The overall system setup consisted of a dedicated machine for each (DB, web, NFS [files]). The former administrator (sysop) was ahead of his time in that he used symlinks for certain directories in moodledata and pointed them to local folders on the web server rather than NFS (which is slow). Folders/Directories like 'sessions', 'temp' etc. were symlinked to (as an example) a partition on the web server called /home/moodledata/. Why? Faster than NFS. About the only thing that really resides on the NFS is the filedir. The /var/www/moodledata folder a symlink to the mount point on the NFS server.
Ok, if I've done a decent job of describing that in words, here's what I did to facilitate the entity restoring 1.9 backups to their 2.3 (last version where one could use a work-around to rid a course of legacy files). In /var/www/moodledata a symlink for 'repostiory/m19backups' to /home/moodledata/repository/m19backups/. From the 1.9 site, a cron job to find and copy all the backups from the course ID folders of that versions moodledata to the /home/moodledata/repository/m19backups/. Did have to setup file system repo in a single course for restoring (only for managers/admins).
One cannot link directly to those files ... still have to get into course, setup file system repo and point to the repo setup for the m19backups and link via Moodle UI. And there are references to those zips in the DB, but they are not in the true moodledata/filedir/.
Try it yourself with just a few mp3's.
Also, you'll have to document for the person who might follow you as it's easy NOT so see that certain folders are symlinks.
Matter of fact, in the latest and greatest 2.7, moodle code is allowing (for certain situations) using directories outside the 'normal'. See the config-dist.php file that comes with that version.
'spirit of sharing', Ken