I think it would be a great idea to try to come up with artist packages....

For example, Herbie Hancock package which include a bunch of his most popular songs (in his case you would probably have to do 3 seperate one, but I know i would buy all three). and you could do pop with jazz it up arrangements that become more intricate in terms of the real track comping/backing/soloing/melodies,etc

BIAB is an increditable learning tool. You could develop these packages with that in mind. It would have mutiple soloing examples for guitar (ie 16th guitar solo, funk guitar solo & blues guitar solo), an example of solo piano and solo guitar arrangements, you could mix up the "real tracks" for backing variations, melody variations, etc. i think you get the idea. That way you have another direction to go with "real tracks" (RT horn section harmonies for curtis mayfield package, RT strings for george benson songs, RT wah wah for marvin gaye songs). You would be tapping the market of students trying to learn (and learn by covers) and instead of the run of the mill book/cd combo that you could buy, you would be giving them an ever changing interactive book (which is what this already is just the different ideas are a little more intergrated.

Ulitmately being able to use real tracks just as you us the midi notation function is the ultimate plateau but i think i understand the difficulty there. for example, frcing a realtracks solo onto a manual melody, or at least showing notation for what the real tracks are playing.

but that is not required for the above mentioned idea, i would like to see:

HERBIE HANCOCK!
stevie wonder
marvin gaye
grant green
jimmy smith
richard groove holmes
george benson
grover washington jr
curtis matfield
mccoy tyner
keith jarrett

i think you get the idea. sorry bout the book
justin