More questions
I would not use an accelerometer because is a single-point-of-failure, better duplicate the touch sensors puting a row in front of another.
You detect the wrong output but what if the wrong output is not a caused by a tempororay condition but permanent defective input or output pin ? the algorithm as you have described it will calculate over and over again and the results between microcontrollers will still be wrong.
If one microcontroller dies, as ignoblegnome said, you must implement something like a ping-pong message exchange between microcontrollers.
P.S.: I am raising these questions in the ideea that some may be of some help.
P.P.S.: Do not laugh, but I think the simplest and strongest design will be a controller built with heavy duty discrete transistors in an electromagnetically and termal shielded enclosure.