Hi Jason! That would be awesome!
No, I don't need all functionality, but what I would love is :
1. Being able to browse by playlist (effectively play a folder - I use my own folder structure) and turn shuffle on/off at will.
2. An easy way to search for tracks and insert them into the playlist to play next - while playing of course
3. Also, when playing a playlist and I hear a track by a certain artist that I like, I then often pressed a button that inserted another random track from that same artist to play immediately after. That for me was the most used feature!! No other player currently does this! Also, when I didn't want to hear a certain artist anymore, by pressing and holding down that same button, all other tracks from that specific artist were purged from the playlist.
4. The Empeg's intelligent search feature where you'd only need to type in a few letters to find what you need because it would limit the possible results based on the available tracks in your collection. (and make suggestions and show you what it thinks you meant). Also when you eg. searched for "Peter Gabriel", it showed the total number of tracks by Peter Gabriel in your collection (well, on the phone anyway) between brackets, and then you could immediately add/insert those into the playlist.
5. A play bar so I could easily scroll through the track (the Empeg does not have this, but it didn't have a touch screen either of course, so it's kind of mandatory now)

Currently I use Car Tunes. While it does have its flaws, I do like the interface. It gives a good overview and is easy to use. It also allow you to search via voice control. That would be a big bonus of course, but I would never expect you to implement such a thing. Oh, I don't really need to see the Empeg interface for nostalgic reasons. Just (some of) its features.

I would also like to offer you to help wherever I can, more specifically eg. if you would need somebody to betatest the app.

Thanks very much for wanting to give this a go!