Hey Bio, have you made any progress with this? I've been interested in doing something along these lines for ages, I always fancied a Steinberger Transtrem, but they're expensive & fiddly so I'm looking at using the Whammy controlled from the guitar. Matt B's Mansons are full of great ideas and made me think about this again. Looks like you're trying to go for the full set of mods? One thing that might be relevent is that Matt uses the Roland Hex pickup so has a 13 pin multicore cable coming out of the guitar already, in fact one of the pins (no.9) in the Roland setup is unused, so that could be sending a control voltage out of the guitar via the ribbon controller (he may just be using the Synth Volume pin 8 as the controller). You need to mod the vg88 to extract this voltage & send it to a circuit which can convert this into MIDI controller messages (see http://tomscarff.tripod.com/anal2midi/****...to_midi_out.htm or http://www.doepfer.de/pe.htm for examples). However, I suspect that controlling a whammy over MIDI might generate a fair bit of zipper noise (MIDI controllers only have a range of 128 steps so instead of hearing a clean sweep you can sometimes hear the signal "stepping" through its settings) but haven't tried so can't say for sure.
Anyone else tried doing this?