Chasin, welcome to the forum!!! I think the waxed boxes will disintegrate pretty quickly since only the inner corrugations are not waxed. If you could find a way to seal the edges, they would probably last a lot longer. If you wanted to create a "bottom draw" system, you could slip a 12" pipe over the top of your current stand pipes. Set the new pipe only a couple inches higher then your current pipe...that way water leaving will be drawn up from the bottom, inside the outer pipe, yet in heavy flow, it can easily top the outer pipe and drain.
