Not sure if this has been suggested, but I haven't seen anything. Now that we have many more Z-levels along the lines of such. Isn't it possible to be able to build more ways of accessing things down deeper, or across caverns without needing to just build floors/stairs. Some suggestions
Rope/Chain: Able to allow dwarfs to climb downwards and upwards, needs to be attached to a base location in order to firmly secure it, able to extend down by adding more of each. Maybe 3-6 per rope? If using rope, has a chance to snap if to much is being brought up down. This idea would be able to be adapted to adventure mode as well, so that one can scale large mountains that have no ramps. Or deep into caverns.
Pulley system: We have a pump system in place already, why not something that would allow for items to be able to be brought across the entire spectrum of the Z-axis? Being able to bring stone up into a fortress from down deep without having to have dwarfs drag the heaviest type of stone would be able to save some time, and give some good experience for pump operators early on.
Elevators: Being able to move up and down locations at a faster pace then being able to walk, whether single elevators, or possible huge 5x5 elevators, using chains and mechanisms to be able to bring down things, whether it be storage elevators that are able to bring goods, or service elevators where dwarves can use to quickly move down the z-axis into depths below, or being able to move across the fortress from a horizontal angle as well. Using a large 5x5 elevator to bring down a food stockpile for hungry dwarfs down hungry in the caves would save them the effort of going up in order to feed.
Bridge: Not really a change so far, but I wish bridges could be used as ramps a bit, like if you properly build it, it can be a ramp up to a higher location rather then just a vertical/horizontal building.