I’m trying to make a cheap manual service thermostat that I can wire inline on a thermostat cable (right inside a rooftop air handler for example) for servicing and testing HVAC equipment. Essentially it’s just going to be a big dip switch where toggling one of the switches closes a circuit between the thermostat R wire and one of the other thermostat outputs (G, W1, Y1, etc.) That part is simple though. The part I’m struggling with is that I also want a switch that can disconnect the actual remote thermostat outputs while I’m using this manual service thermostat. I could just use another large dip switch and manually toggle off all of the outputs one at a time but it would be nice to instead have a single switch that toggles them all off at once. The problem is if I only use a single switch then that means I need to open 3-9 different circuits (G, Y1-Y4, W1-W4) with one switch. I haven’t seen any 9P1T switches available anywhere. I know there’s all sorts of things I could do fancier circuitry to achieve this but I want this to be as simple, cheap, and robust of a device as possible.

Is there a simple and ideally entirely mechanical way to open several low power circuits with a single switch or am I just stuck using multiple switches?