Personally, I think there would be TOO MANY features requested by users to put in one box and make it affordable...
A few years ago on this board I offered the idea that the way to satisfy users would be to make the AKB 'Menu Driven' in that there would be a basic model that is sold and a list of options that the user would select on-line to D/L to the keyboard ...
But this might hinder sales of 'new' models which the manufacturers would not want ...