(cue Beethoven's "Ode to Joy")
By Jove, Sir--I think you've got it! NICELY DONE!!!!!!!!!
Just to clarify further, I have enclosed two images: first, of the original vexing section of the schematic; and second, a (busy) markup showing the connections of the "Frankenstein" switch. Is it correct?
Elegant--once you know the trick!
Many, many thanks!