Oh no, heck no squared. Because if you do, that means that every macro has to publish any symbols-in-functional-position it actually creates. And every programmer has to check every macro he or she uses to make sure that any local variables he or she has do not conflict with the symbols-in-functional-position published by the macros. Hades breaking loose and all that. Funny action at a distance.
As for redefining a macro - then let's implement 'macrolet, that way we don't have capture.
