I agree that what you propose would be better than nothing, but it will still be lacking.

Assuming the software can get there, we also need to add more sensors. The head nods, eye contact, subtle facial gestures, and other body language that are such an important part of a collaborative jazz ensemble will have to be sensed. However, even if the computer can be enhanced with sensors, now you've got to communicate from the computer(s) back to the other players. So, either advanced robotics, or ensembles adapt other signaling schemes that the computer player(s) can engage. It is not a simple problem even if AI can made to be "creative" and "musical," that is not the whole story.