This might be what I've been looking for. On the first of every month I have Hazel put everything in ~/Downloads/yyyy-mm (previous month), with the intent to move each file to the correct project/area folder in my actual file structure. But I'm about 1.5 years behind on that...
Have you looked at competitors? If so, what are they? I haven't found anything that does this as elegantly as Fallinorg.