Since MIDI is barely implemented, there is even less reason to have a chart.
In order to be classified as standalone and a studio centerpiece, I would think a traditional MIDI chart should have almost all option checked as implemented. Today, I think it would be difficult to check much of anything. I mean, channels are pretty much non-existing, and that's a pretty basic MIDI concept.
However, last I read from Akai, was that the core or underlying layers are now in place and the upper layers can be put in place, and hopefully we will soon be checking things off that chart.