FWIW, I've been noodling around in my brain on this concept. (After a 13" snowfall here in KS, I've been house-bound since last weekend. At my age, shoveling that much snow from my driveway is just asking for a heart attack...lol!)
The tepid response here (and the apparent lack of commercial products) might indicate there is little interest.
I can imagine a DIY building block system that could be used for OTB mixers, or a sub mixer for a synth rig. I even poked around at Mouser checking out prefab wiring solutions to connect front panel parts to a PCB(s).
shrug.....
Bri