A few years back, I re-wired the electrics in my guitar using a semi-complicated setup of a 6 way switch for pickups in-phase or out, and parallel or series, tone and volume pots, and distortion. There was also some choice to be made about what capacitors to use, and picking a diode for passive distortion.

After a first pass trying to just wire it directly, I ended up hot gluing a tiny breadboard into the compartment. That went much better and allowed me to swap candidate parts until it was right.