This seems a great way to simplify the UI across levels, as well as duplicate backgrounds!
However, I don't think this is any good for paralaxing because anything and everything you add is also added to the next inherited layer, which is just a darker clone.
I would think it is best to just make your layers and detail them how you want, then hide them to continue working in the main layer.
Upon reading the above again, I think I nailed the "that's obvious" parts. Hrm, ah well!