[x] Vref net requires a pulldown (2.4k seems to be working fine) in order to drain the charge to 0V when the MCP1501 is shut down by the MCP23017. Without it, Vref basically floats, and the the constant current goes undefined.
[x] Voltage dividers on +15V and +48V to turn them into inputs for the IO expander, so it can check that the supplies are working.
Noncritical
[x] Increase the space between the Qwiic connectors to ease hand soldering.
[x] Bring the I2C bus out to a 0.100" header.
[x] Still need more space between the individual string screw terminals/headers and their corresponding indicator LEDs. It should be sufficient to bring them in towards the middle by 0.5mm, which should roughly line them up with the courtyard of the mosfets.
Noncritical