I just wanted to bump to this post, it's a nice discussion and I shamefully admit I didn't know how to change voicings until I read this post. Custom chord diagrams would be incredible, I'll tip your devs! haha. There are some artists, such as Dave Mathews Band that have unique voicings of chords that really impact the overall sound. Custom voicings would allow for better education, better SATB part writing, remove overly difficult redundant notes, allow for more creativity by avoiding cliches, etc...

It's a bit of a digression, but I have a similar problem when converting sheet music to guitar tablature. The computer often doesn't make wise decisions, and I have to comb through decisions to make it flow better on guitar. Be nice if someone wrote a tabbing script that taught the computer to make wise fret number decisions. Similar shapes are prioritized to take advantage of perfect parallel motion. I'm not the biggest fan of 6 or 5 note guitar chords, for a variety of reasons that would maybe be too lengthy to explain. Joe Pass is excellent example of the 4 note chord style I'm thinking of.