I like your idea, Nick; I've thought about this before and would have used generic-sounding names ("string", "flute", "hybrid", "reed", "auxiliary" for any oddballs, etc.) but visual pipe profiles is an approach I never thought to consider. I imagined that if I were to use this method for my next project, I would go with a minimalist stoplist for the tablets/drawknobs/buttons so that, whatever else, I would have the diapason and flute choruses covered, a mutation or solo mixture, a pedal reed or two, and maybe a string celeste. What are your thoughts along this line?
Lieblich gedeckt, gedeckt, clarion, salicional? Somehow it seems as though it would "feel" better if the higher pitched ranks had smaller icons - maybe not quite to scale, but enough to immediately see that they are not 8' ...?
Or maybe just a different color font for each tone family - then all you would need would be the number ... though I wouldn't want to have to include a legend that somebody unfamiliar with the instrument would have to memorize.