Funny you should ask this ... been cleaning up a Moodle site (major space issue) that has been neglected for a couple of years now and teachers have been pretty much on their own. As a result they have been doing what they can ... backing up their own courses. That's fine for 1 teacher per course, but for 'team taught' courses (multiple teachers with equal access to backup), it presents an issue. If a 'team member' (in your case) backs up the course, the backup file is saved into their private files. Only way somone else can get to them in the Moodle UI is to login as them. Pain in the arse cause you can't logout cleanly and retain your higher access level account active.
On Linux and have command line access? One could use admin/cli/backup.php script and point to a directory outside of Moodle, or to a file system repo to which the course has been setup to access. Have one site set up like that. It works, but do have to manually check space from time to time and if getting towards 'un-comfortable', remove some.
Could run a bash shell script to use the backup.php script (which takes defaults from config of backups) and cron job it ... cron not part of Moodle cron, but a cron job outside of Moodle.
Again ... got Linux? (probably could do this with Windows too, depending). Could spin up another Linux box to act as backup box ... could create a mount point (doesn't have to be a permanent mount) for it in /moodledata/repository/ and then through a home grown process (cron, etc.) run backups that way as well.
Lot's of tools admin level persons could use to admin the site haven't really been developed yet. Would be nice if they were core. ;)
'spirit of sharing', Ken