Test box
Found a big aluminum enclosure at the Baco perfect for a test box. Based it on this article and some bits from this forum thread. And had a big DPDT lying around I could finally make use of. But since it's a DPDT and I've used it as a true bypass switch I've added a Millenium Bypass so it also switches a LED.
Millenium Bypass
For switching a LED with a DPDT switch I added a Millenium Bypass circuit.
Probe/oscillator
I'm planning to add a switch to enable probing with guitar input or with a simple oscillator based on a 555 timer chip.