Spindle switch box for CNC 20mm section mounting

I've got a cheap Chinese 1610 desktop CNC router, which is really excellent value for money. However, I decided for safety and convenience that I should be able to isolate the spindle motor from the power supply, such as during tool changes and when using the motor power feed with a laser module.

I also wanted the switch away from the motor to make it safer to use if the machine is in use when isolation is needed. That seems quite important as having hands near a working cutter/tool isn't a goo