I agree with your progression, with a little more detail: * emulators on your desktop * harware like a RPi and maybe add dedicated USB controllers * cardboard

I agree with your progression, with a little more detail: * emulators on your desktop * harware like a RPi and maybe add dedicated USB controllers * cardboard mock-ups (I use particle or panelboard for mounting the controls) * permanent version in wood, metal, plastic, etc. FWIW, I find the screen bezels and access points (doors, etc) the trickest parts. Mock-ups let you experiment with the dimensions and size easily.