Its still loud enough even. Took me 30minutes to solder those stupid 0.1mm magnet wires
Found the battery monitor guide by Robbi_Blechdose and ordered a few Attiny85's and a programmer, should easily fit in the empty space at the bottom
I played around with the retroarch config and found a few useful tweeks:
Changing hotkeys for save/load state to "up" and "down" so you can actually save states without the L/R buttons
Changing aspect ratio to 1.25 and stretch to true so that gbc for example at least gets the full resolution in width, the bit of stretching doesn't really bother.
Also the gui resolution to 160x128 so you can actually read the osd text.
Adding smoothing to make text muuuch more readable!