On the practice menu could you add some controls to allow some choruses to be played with the harmony parts dropping out for a while. This will enable practicing trading fours etc with the drummer which helps to develop an awareness of where you are in the chord sequence even when the chords stop.

I suggest two new controls:

Practice: No of trade bars - can set to any number but typically 8, 4 or 2
Practice: Trade bars every nth chorus - can set to any number

So for example you could set to trade fours every third chorus

As a further enhancement it would be great to have some enhanced drum fills for trading!