I'm going through the videos at the moment, at episode 8. They're really great, it is fantastic to see the amount of thought and planning that goes into a design, and the patience of a small group of dwarfs working on a megaproject with the world burning (freezing) around them, eating their little plump helmets and drinking their dwarven wine. The surface can wait, no?
Anyway, I was wondering why you go through the bother of setting up water reactors when you have a nearby aquifer. Wouldn't it be just as easy to drain from the aquifer to the map edge, so the water gets 'flow', and put wheels over them? Or do reactors have some advantage that I don't understand?
Another thing I don't fully understand is why you go through the bother of creating a holding pattern loop and the use 1 lever per two torpedoes, when you might as well use one lever per torpedo and control the release rate with the levers? Or is that for the thrill of being able to say "fire torpedoes 1 and 2!"? [EDIT: never mind, you want two mine carts circling the track simultaneously and the 100 ticks are about right to get the to be on opposite sides. Which I'm sure you knew before starting construction ;-) ]
EDIT2: but I do have another question: you are very concerned with blocking up the cavern part of the route, assigning everybody to masonry etc. In such a case, I would set up a block stockpile nearby and make sure the masons are around with a burrow. Why did you do it as you did?
Back to the videos, can't wait to see the OMG in action! :-)