Hi to all,
first of all thank you very much for all the comprehensive feedback. I appreciate it a lot.
As Chicken mentioned, this BoosterPack is not supposed to be used as a regular MP3 player. It's more like a general audio development platform which supported a buch of codecs. For those who are interested to work with audio it can do pretty much everything from simple playback/recording, GUI design to complex signal processing and digital filter design.
The idea came up when I build a Christmas pyramid controller for my dad last year (see here if interested: https://drive.google.