Looking at your sandbox, it appears that you have been thinking the same thing that I have been thinking (for quite a while actually). It just hasn't been high on my list of priorities and I haven't spent a lot of time here lately.
I just want to let you know that I have a Bot that I could use to make the changes quickly and all at once instead of manually changing them.
So I like your thoughts, but I also hope that you would have run it by me before you went ahead with any changes of this magnitude.
I want to taka a good look at the Category hierarchy and see if there are other changes that should be made, so let's hold off for awhile.