Hi Spotty, It looks like we are on a similar quest. My Viscount 350, with a one octave pedalboard, which I am converting into a 32 note pedal.
I also looked at your sulution, using a cheap synth with midi. Sadly these are quite rare here in France. So I opted for the pedalboard encoder from Sound Research.
My pedalboard is "home made", using magnets and reed switches, the most difficult phase of the project.!, as for the voices, with this organ, there appears to be several options!
Non of my endevors, either mechanical or electronic are origanal, just an interesting project to try and capture my past as an organist.
I will continue to post as my project progress's. In the meantime, it is very interesting to follow your progress.
My regards Raymond
Ps: I forgot to mention, I am in the proccess of designing a bit of hardware for easy voice selection from the pedalboard, for use with the Sound Research hardware and possibly other. When its finished and debugged I will post it for anyone interested. Further regards Raymond