Thank you for your well-intended suggestion.
It is not, however, practical. Allow me to explain.
All editors start at the bottom, in very small categories, this allows us to minimize any damage borne out of inexperience or malice. It also give the new editor an opportunity to learn their skills without getting overwhelmed in a huge category that is overflowing with suggestions and spam.
As an editor gains experience, he or she is encourage to apply for additional categories to edit, either higher in the tree or in different branches of the tree. Remember, the named editor of a category can not only edit n that category, but automatically has the right to edit in any category further down in that branch of the tree. Thus, when an editor receives the right to edit in a new category, it may well mean that the effective number of categories where they can edit more than doubles.
Having two editors with dissimilar interested and editing skills would do both a disservice. Both would be taken out of their comfort zones, both would need to get a lot more assistance than they are used to simply because while one might be a whiz in regional, they may not know the things that make shopping unique.
Plus, what if an editor simply does not wish to edit someplace else. Is it worthwhile risking the loss of their services? Even experienced editors with tens of thousands of edits tread very carefully when editing in parts of the directory where they are not familiar.
Perhaps this will help put it in perspective: I was recently promoted and am allowed to edit anywhere in the directory. I was honored, but before my head could swell too much, I got an e=mail from an editor I deeply trust. The gist of the e-mail was "even though you can edit anywhere does not mean you should edit anywhere". I've taken that advice to heart and have only slightly expanded my comfort zone in the last few weeks.
On a personal note, even though I don't believe your idea can be implemented, I want to thank you for taking the time to conceive it and to share it with us. It tells us you care about the directory, and that is very important ot all of us.
I'm now editing in an area that I'm unfamiliar with, also, and just like gunner, I'm taking it a bit slow while I learn the ropes there, every part of the Directory is a little different I think.