If I was going to make a CD player, the feature I would need to add would be the ability to play compressed audio (particularly ogg vorbis) rather than just standard CDs. Because you can fit so many more songs. Music via DVD-RW data-discs would be cool (or some mini disc equivalent? never had those though).
Though even a music player (no disc support) w/ogg support would be nice. I asked for this as a gift but as expected what I got only plays low-bitrate mp3 (I don't feel like converting/managing my albeit small music collection, though I have thought about getting some ambient OST stuff instead if the quality wouldn't ruin it).