So, I actually kinda dislike a lot of the more automated suggestions in this thread, but playing with .31.0X has made me want to get on my pulpit and trumpet the importance of one particular thing that's been mentioned here: Lifts. Having your smelters 150 levels below your fortress tends to consume rather a lot of haulers.
I'm talking about a pair of workshops, a lift base that can only be built on solid ground and a lift platform that can only be built over a 3x3 channel that extends downwards any amount but has at the bottom a lift base. It would consume ropes or chains proportional to its depth, and the "top" building would require power. The platform could then change position when a dwarf entered it from whichever end the platform was currently at. The platform would be loaded and unloaded by haulers, presumably up to a maximum load limit. The dwarf would stand on the elevator and raise or lower it. I'm not sure how you'd make that dwarf pass *through* the space between the two buildings, without a buildings rewrite I'd suspect the operator would stand in one place then teleport to the other after a particular amount of time, but if multi-level buildings became possible, the operator and the "platform" could pass through each level of the shaft and then arrive at the destination.
I'm not certain how deciding what should be put on the elevator would be handled - I suspect one option would be to make the lift count as a sort of stockpile to which hauler jobs were generated, and on arrival at the destination - top or bottom, the lift would then be emptied according to the "take from" orders ascribed to its stockpile settings. Messy, given that dwarves would have to know not to take things from the stockpile before it had been moved, and there are also some issues with starting to load the stockpile before it's been "unloaded", so I suspect this would be a custom implementation of a lot of things, and possibly not a high development priority for Toady as a result. At least not until buildings rewrites, or hauling upgrades, or the Caravan Arc or whatever.
But I think, given that how far away my forges now are, it's suddenly more important that we have a way to move items long distances over the Z axis. They're certainly period - they were mentioned by the Roman architect Vitruvius, for example. Also widely used for transporting ore in early shaft mining. Whilst not in widespread use in the real world for carrying parts and products until well into the industrial revolution, parts and products didn't tend to be constructed deep underground in medieval times, and it wasn't until production lines and factories that moving large amounts of goods up and down long distances was really necessary outside of mines.
Anyway, I think this falls sort of between this issue and the improved hauling suggestions. I thought I'd post it here, though.