I made one in a similar way this past summer -- been meaning to post it, but work and holidays and little babies got sort of crazy.
8 knobs, 2 buttons with LEDs (on separate gpio pins so not hard-wired to button state), 3 stomps, 3 leds (own pins), and 2 1/4" jacks for expression pedal input or sending output to pedals that accept the 3.3v CV. Graphics are just an aplpied acetate which isn't my favorite, but it works and hasn't been damaged so far. Cut the I/O of the enclosure with a dremel tool and cutting wheel:
Added the small bracket to help hold the board tight to the enclosure and reduce stress on the connections of the midi jacks.
Recently picked up another Core and wondering which direction to take...