OK, after serious consideration my priority has to be getting the #$%^*&^%$#@ing machine actually working so I can make some stuff with it. Playing about with circuit ideas is fine, but...

I'm not wasting a long weekend off work waiting for RS to send me some new cable and other components including 2mm pitch plugs for the PCB headers, so I've made a circuit board which connects into the existing screw terminals without the need to remove/replace surface mount components on the BOB itself. I expect it's going to work. If so, it'll do for now and I'll make a more reliable change to the wiring later. This machine is after all just a toy in my shed rather than the heart of a commercial operation.
Watch this space for details if it works!