In the tradition of Star Wars...why not do a prequel, instead?
I think there are some plot(s) that I'd like to see...
How did Munkustrap got the leadership of the tribe?
What caused Macavity to go bad?
What caused Grizabella to leave the tribe?
It would have to involve the CURRENT Jellicle tribe for the plot to work. Another idea was to submit stories for a "prequel" to ALW, and it would be neat if he would be able to dream up new songs and dances.
Of course, the plot would still have the "Choosing" and the Jellicle Ball! (can't get enough of that music and the dancing, there!
I think that's all I think of for now.