This looks like an interesting project, but i would of thought that the transducer would have been integral to the actual pedal so can't see how this is going to work, if you could explain how you intend to do the modificatation that might make it clearer, you also would have been able to do any machining on a manual lathe only advantage of CNC is speed, but you could have sorted your prototype, i have a set of IQ2 powermeters on order that are similar to your first set of road pedals but would prefer SPD if you think it's viable.
Regards
Mike