I have confirmed part of my theory on this. I read in these PDFs that when the brake pedal is pressed it automatically disengages the ASR system and switches to using the ABS system. Also, there is a different brake light switch (4 pin instead of 2 pin) used on ASR, ASD, and 4MATIC equipped cars so that the car will disengage these systems and instead use ABS to control wheel slip. So, the extra 2 pins on the 4 pin switch are only there to tell the ASR to disengage.
Now, I need to find out if simply bridging the connection between the 2 additional pins will in fact disengage it or if I have to add voltage from somewhere else to trick it.
I think this will be a way simpler way to disable the ASR on W126 & W124 cars if it works. Any thoughts will be appreciated.
http://www.w124performance.com/docs/mb/other/ASD-ASR-4MATIC-ADS.pdf
http://www.w-124.info/w124/ASD-ASR-4MATIC.pdf