A graphic representation of Das Wohltemperierte Klavier

I was looking at this video and I started to think that it would be nice to have some graphic representation of the fugues. Like a piano roll or something, that emphasizes only the themes, when they appear in different voices at different pitches. And the counter themes and the 2nd themes. It would flow as a transparent piano roll on the video.
The steps I'd take to achieve this would possibly be:

1. A plugin that coloured certain note heads in a score. I'd mark, say 8 note heads. Then I'd run the plugin, which would colour all 8 notes, starting with a chosen bright colour, then fading to black. With this plugin I could colour all occurrences of the themes. A score like this would in itself be already very informative (and nice looking).
2. To the next I'd want to export the coloured sheet to midi in such a way that all coloured notes would export with velocities proportional to the brightness of the notes. And all black notes would be deleted. A midi file like this would in itself be a fun thing to listen to. It could also be mixed with a normal audio export of the original sheet.
3. The following thing would be a midi player application that would turn midi data into an animated piano roll. The coloured bars that represent the notes would have an opacity proportional to the velocity, fading to black.
4. The animated piano roll would be fairly easy to capture to a video and mix with an existing video, making the bars in the piano roll appear opaque or semi-transparent. There are some free video editors for this.