The first few posts here will summarize discussions which have taken place on the ww-devel mailing list around this topic.
Here is one of the possibilities which has been talked about -- namely to keep the basic structure, but to revise it.
I think everyone agrees that the current system should be improved. People have been allowed to add new subject/chapter/sections dynamically, and that led to topics being represented in several different places.
One could keep the basic structure which is meant to mirror how people go about picking problems from a textbook. One first picks the subject, then the subject has a list of chapters, and each chapters has a list of sections. Naturally, we would refine the current classification to remove redundancies, make sure problems are in the right place(s), and then make it so that one cannot add to the system without a level of editorial review.
In some areas, the breakdown of chapter/section within a subject may need to be rewritten, and this would be done by getting interested faculty to select a new set of chapter/sections for that subject.