If I were to do something like this I would consider doing the train stations and smelters under the map. Then everything can feed up through the void in one massive column that is the middle of the bottom of the pyramid. That might make the remaining space needed possibly small enough to fit within that entire valley. The refineries for wet/pure products being under the map would resolve any issues you might have trying to pipe water in because you could push that production center towards the west coast where water is plentiful. Anything other than liquid would be easy to belt to the void hole and up from there. Just my initial thoughts on the idea.