Stacked chords vs slash chords and why both are important
It might be good to implement stacked chords in addition to slash chords. Stacked chords are not cosmetic. Stacked chords are a different way of expressing complex chords. For example, Bb13b9#11 can be written in stacked fashion like this:
Same exact notes. Here's a grounding theory on why this might be preferable. Basically it's called "chunking". In the first example you have a chord (Bb13b9#11) with 7 distinct notes. In the second example you have the the same notes, but they are referenced as two "chunks" played together. The idea is the brain can more easily handle 2 chunks of something better than 7 individual units. Hope that makes sense.
See the new 2016 "Real Book - Enhanced Chords Edition" by pianist David Hazeltine. He gives a short explaination of his use slash chords in the forward.