BTW n5926g, the membrane switch has both sides insulated from ground and metal in the airbag assembly and both wires on the connector carry out into the harness, no local ground visible. So the issue with these horn switched is that it's an internal short in the membrane switch that causes this, it is VERY unlikely the aluminum tangs on the emblem could pierce both layers of copper-clad mylar (or whatever the insulator material is) and even if they did, the membrane is laid between two plastic parts, no metal there, except where the two torx screws that screw into the airbag metal trap it and the steering boss cover via a metal plate that also is the horn connector bracket.
Sorry but the horror is still fresh in my mind.

But since I'm sure you're right about it being a grounding connection, I was going to use your suggestion of running the relevant wire to a cheesy switch - or maybe an old-style overhead lavatory chain - if I couldn't fix the thing.