Just saying.
(oh, and the possibility to sweep from the left to get to the course list was great, the removal of this feature was seemingly unnecessary)
Maybe youtube links so they do not need to host the terabytes of video files. But I think audio takes you far concerning user-created courses so do explore that.
In order not to flood the servers, a fine point, I would simply go for including the Multimedia Levels feature in the mobile app.
Audio is great, agreed, but videos could make for a more memorable content (cf. the official Japanese courses) 