There was a real desire to combine the shutter & focus into a single pedal & combine the circuit board with the pedal instead of requiring a long wire.  It would be easy enough & more transportable by buying a sewing machine pedal, but lack of space to store another pedal encouraged modifying the existing pedal.  The existing pedal was never used for anything besides a camera shutter in 15 years.

The decision was made to start sacrificing it. 

The original sensor used 2 carefully bent reeds to disengage at the halfway point.  There was a place for 2 more reeds to detect a 2nd offset but lions don't have the tools to make such precise reeds.

The 3/4" range of motion of the pedal was divided down to a fraction of a mm.  A common theme in musical instruments is to divide the range of motion to the smallest possible movement that can be detected, using reeds & levers.  Not sure why this is.

There were more holes for mounting other kinds of sensors.  The same parts are used in many different products.

The easiest sensor seemed to be a magnet hot snotted near the bottom with a hall effect sensor on a new platform.  It would detect the full 3/4" range of motion.

Hot snot seemed to stabilize a magnet.

Many test prints yielded a sensor platform that could be screwed in.

It was set it in place to mark the holes.

Then it was screwed in from outside.

The magnet & sensor viewed from outside.

The firmware upgrade found it generating 5-115 on the ADC.  It managed to differentiate fully raised, focus, & shutter.  It burned 100mA doing nothing.  The mane problems are the obsolete LED & radio being used to reduce component count.

Testing showed the LED was essential in feeling where the division point was.  Being able to see the viewfinder would help.  Lacking good enough eyesight, the next best option would be an aural cue.  It was definitely the best pedal control of all of them.