Could you not just find a defrost switch (super cheap used) and switch the face with your ESP one?! Quickest/easiest IMHO.
What wiring are you planning to do to disable the yaw sensor? If I remember correctly the only wires from the yaw sensor are 4 wires that go directly to the abs module. You planning to interrupt those?
Yes, I plan on unplugging the normal esp harness to the dash switch and stuffing it in the cracks behind the dash. Then getting a new switch (while switching the face with the ESP button) and using it to interrupt a wire or two (of the 4- correct) between the YAW sensor and the ABS module. As far as which wire it may not matter as any one will most likely disable the system... however I'm going to unplug it and check for voltage with a meter, once I find it I'll break that one. That way when I hit the "new and improved ESP" switch it will throw the "triangle" dash light like normal but not only will it kill the traction control it will also disable the ESP portion of it" but NOT disable the ABS. Hit the button again and you back to factory. Same as when I just unplugged the yaw sensor and plugged it back in the light came on and went right back off (only thing I didn't test is doing it while the ignition was on... I shut the car of to get on my back and plug the thing back in... but I believe it will work hot also... The only difference is the light will be throw because the sensor is not working and not because it's in "spin your wheels" mode.
96-02 Audi A4 S4 A6 S6 A8 Fog Lamp Switch Part# 4D0 941 563. Should be able to search completed listings on ebay if you want a pic. Now, I don't know if it will be perfect but I took a chance on it. It was $15 bucks same as the defog switch. The problem with the defrost switch is that it is of the 6 terminals on the back only two of them function as a switch when checking with an ohm meter. Naturally they are normally open and when you press the button to make those terminals close. However the switch is depressed slightly and I would have to stare it the slightly depressed switch during the 98% of the time I had the system working like normal and it would bug me. My hope is with the other switch that I might get lucky and have one set of terminals that is normally closed or at the very least have it not stay slightly depressed. I figured that at the very worst it would be the same as the defrost switch. As far as staying depressed or being normally open so I would be no worse off. Give me time to get the switch in and wire it up and I can come back with a full report.