Create "twitch radio" that is composed of user submitted original songs
Create an interface for indie musicians to upload their tracks with the understanding that they will not be paid royalties or be able to issue DMCA complaints if they upload. Give the people who submit songs a tracking dashboard, maybe other rewards if they get enough plays/hits/likes. Maybe also allow viewers to downvote / upvote songs.
Give streamers a spotify like interface that allows them to select genre and skip through user submitted musical content easily.