Then I want to grab all the files and put them on S3 or something and store the links in the db. Then it's a front-end problem, I'll need a command line interface and then one day I'll make a GUI. I could also find tracks that exist only, say, on YouTube, and store links to those too.
Then I'll be able to use it as a music player and store no music on my local machine.
Then the biggest pain in the ass becomes syncing to my portable devices, which is the only reason I haven't done this yet. I would hate to have to maintain two libraries at the same time. So I have to think my way through that. Though I'm sure I could write a syncer that would work much better than Google Play's, I haven't bothered to sit down to do it yet.