here's my effort:
2x axolotis in series inside a koma field kit box.
the 'front' axo is intended for synths, samplers, sequencers etc and has the lower oled, two big knobs, the joystick, the 5 thin pots and the 5 buttons.
the 'back' axo intended for loopers, effects etc has the upper oled, the four top pots on the right and neighbouring buttons.
in addition I have a teensy 3.6 inside, with another oled strip, as a controller that sends midi to both axolotis and is controlled by the two encoders and the 2x 4x4 button matrices. I intend to create some useful arduino apps for that as the matrix buttons are best used to trigger macros rather than as a playable musical keyboard
I also have a SAM2695 midi GM synth board inside so as I have a simple optional sound pallette to drive with midi.
just finished it yesterday and apart from my crude aluminium cutting skills, it works very nicely.
power comes in through a DC 9v - 12v plug with an on/off switch in the case and distributes to the axos and 5v to the teensy and the sam2695.
I don't think i'll fit anything else inside as it is a birds nest of wires already.