I’ll keep replying to myself as there seems to be a bit of interest.
I did the rewire a few days ago and I’ve been A/B testing amps since then. So far so good. It was easier than I thought, no soldering. I just rearranged the pins in the interface plugs.
If you’re confused as to why that would work, realize that there are 5 wires going to each of the four pairs of TRS plugs. LR for each of the plugs and a common ground. The ground is also common on the switch side but the other four wires are switched. In fact the board for the switch is labeled XLR Balanced Switch so I’m sure it’s the same one Douk uses here: https://www.amazon.com/Nobsound-Audio-Balanced-Converter-Selector/dp/B07QVKPR2V. I simply disconnected the ground wire and the LR wires leading to one of the plugs and then connected the ground wire to where the L wire used to be. Because I did this on both the inputs and the output plugs, the common ground in the switch is no longer part of the circuit.
If anyone wants to make the same mod and needs more detailed instructions, just let me know.
Next I’m looking into a unit with an IR remote and speaker terminals. I plan to make adapter cables so it can be used to switch both single ended and balanced headphone connections. Then I’ll probably whip up some IR transmitter on a computer to randomize which input is used so I can blind A/B test. There are a couple of units I’m considering. I’ll post here if/when I choose one.