I don't care about a 99 track limitation, I won't use it that way.

My point in writing that wasn't to say "if you wired the empeg up that way it would be limited to 99 tracks", because there's no way to wire it up that way. The empeg doesn't work on a CD/TRACK system at all and doesn't have any provision for doing it that way.

On the other hand, your head unit's CD changer interface totally revolves around the CD/TRACK system and is inexorably hard wired to do only that. So in order to control the empeg like a CD changer, you would have to invent some kind of a complex translation layer between the head unit and the empeg. Such a translation layer would have to be a clever combination of hardware and firmware, whose only job would be to dumb everything down so that the empeg was little more than a glorified CD changer. This would essentially negate all of the cool features of the empeg. So if you're going to go to that much trouble and expense, why not just buy an MP3 changer product which was designed to work that way from the beginning.

It just isn't very "me" of me. I know it can be done, just giving a shot to see if I can figure out how.

Well, if you really think you can pull it off, go for it. If you can get pictures, schematics, and documentation, we'll write it up and publish it. Because it would be one HELL of a hack.

I also saw that the team has made such controllers before. If so, any hints as to what went on?

Yes, they built an "MP3 Changer" product for an OEM. It was a completely different product from the Rio Car although it shared some similar software and hardware bits. It never saw the light of day, as far as I know.