The stuff above headed me in that direction but using the chromatic keyboard. (I've been playing in scales - amazing how songs just emerge when all the notes are correct-ish).
So I did a couple of simple chords on a guitar-like diagram using the number system above.
The first two are here: http://eigenharps.blogspot.com/2010/07/alpha-chromatic-chord-shapes.html
Do click on the image for a readable size. Knowing how to construct chords lets you build more complex versions from this starting point
Then John Morley asked for a more interesting example and suggested a tritone substitution.
So I did this one: http://eigenharps.blogspot.com/2010/07/tritone-substitution.html
I learned a lot going through this as an exercise.
This leads me to think that I'd like to be able to add a control keygroup, which could be left at the top like the scales and root group. It would have keys for each root and keys for chord types (major, minor, etc). This would be used to light patterns in the playing (chromatic) key group. Select major, push c and CEG based on middle c light red, all other instances of CEG light green. While I'm being bold, I'd ask to be able to *record* this control keygroup. Note that I do not want this to actually sound anything.
The result would be visually dramatic - in effect you are using the keyboard to visualize the chord progressions of the song - and it would afford the player chord diagrams superimposed on the actual keyboard. The latter might be interesting in improvising lead solos.