Am a Linux person ... but ...
Course backups, correct?
Could mount a remote storage device D:\data\ and in config of Moodle set course backup preferences to go to a designated destination and provide path (D:\data\).
Moodle will still use moodledata\backup\temp\ to build a course backup but the very last thing code will do is copy that .mbz file to destination.
That might be a catch 22 for Windows ... size of a file that can be copied ... as opposed to 'move'.