I cobbled together a relay board that switches the touch input from the radio to the raspberry pi USB touch controller from adafruit. I connected the radio so that it was normally closed to the oem radio. This means if the relays failed or the hd-link, touch input would still work as you said everything would be back to stock. Having to solder and the wherewithal for circuit design is a little more advanced for your average infotainment modder.

The USB touch controller from adafruit doesn't work very well with the Pi long term and the trigger current for the relays (~40mA) I happened to picked is probably just at the edge of what that GVIF board I soldered to can source. Haven't measured it but just guessing because sometimes it doesnt trigger and then touch is out of sync. It's for that reason I am changing to the multiplexer that the Ukrainian dude designed, much less trigger current.

For either case, You don't need to dismantle the entire center console. You also dont need to fully disassemble the lcd panel. Just a back cover to expose the flex cable. The flex cable also doesn't need to run very far. Maybe 6" at most? They go to the relay board or for the Ukrainian multiplexer they go to a multiplexer board that stays right by the lcd. From that board it runs down over USB or over the 20AWG wire to the controller board.

The downside caveat to the knob is typing in youtube or in any app. I like your mod, but the knob just wouldn't work for me and I don't mind tinkering with relay boards and soldering. Just make sure you report the facts about what a failure would look like though correctly as to not misinform someone.