[bread_baker]

I thought your post was interesting. I used to have a Moodle website (but it was deleted) and I was going to start uploading audio recordings that I was going to make. I bought the recorder and experimented with it. I wanted to give the students listening exercises that they could use over and over. Someday I may try it again, but this is not a priority for me.
Post again after you've tried out your idea, and tell us how it works!
In adult education, one big concern is attendance. If you give the students a way to make excuses to not come to class, some will take advantage of it. That's one reason why I didn't make my project a top priority.