So, quick sketching:
Pin 12 of the Teensy is used for MIDI Out (that’s up for grabs), I2C broken out, switch to toggle standards, labelling on the PCB.
The obvious thing that is wrong here is that I’d rather the jack connector and II connector were on the far right edge, pointing out sideways. The reason I haven’t put them there is that I think I need EAGLE Premium to be able to do so - like, the board doesn’t fit into the 160cm^2 limit of even EAGLE Standard. SIgh.