Theoretically, let's say a modder released a patch for both Pokemon Sun & Moon, that included an actual Hall of Fame (Pokemon X & Y), as well as the ability to rebattle trainers already beaten. Would you be able to add this patch to your own copy of the game (and still use Pokemon Bank)?
So long as the actual Pokemon aren't altered past recognition and don't interfer with online play, it should in my opinion.
So long as the actual Pokemon aren't altered past recognition and don't interfer with online play, it should in my opinion.