custom firmware for MP3 Player

I'm looking for a good MP3 player (hardware) that you should be able to create firmware to remove certain option like (FM Radio and Playing videos) so it can strictly be used as an MP3 player.

So I'm looking for 2 things:
- recommend a good hardware
- create custom firmware to remove radio and video

I will need to know the recommended player in advanced to make sure its a good quality