from playing the game during the last world, I believe I have an idea of how the mechanics work, so here are my thoughts:
Elevators *could* be used to travel the vertical distance in the world, but they are not and I think will not be used for that. They cost way too much and require way too much manual labor to install that it does not make sense to put them in mines. They require enormous amounts of steel, as well as diamond and mese blocks. The steel is a valuable resource that does not justify using it on the elevator. They also do not give instant transportation to the destination… they are still pretty slow. Instead, people either just use ladders with a falling tube, or they use nether portals for deep mines.
However I don’t think you should remove them, they make nice additions to the construction aspects of the game. You can have skyscrapers with elevators, or rooms underground accessed by elevators. Its a cool thing to have, as is demonstrated by the tower structure at spawn.
rails– perhaps adapt minecart (https://forum.minetest.net/viewtopic.php?f=9&t=22464&hilit=cart) by joe7575? It has automated carts… its similar to a low-lag version of adv-trains, in that you can pre-program carts to show up at certain stations.
perhaps have mini-trains that use the regular rails?
Moving down a long shaft is boring. It is boring to go down a 10000 node ladder, it is boring to go up it, it would be boring to build a 10,000 node elevator, and it would be boring to ride a 10000 node elevator at the speed that they move. Teleporting in some way is a major part of the game that makes it playable. Currently, we use nether portals to teleport vertically. I like the nether portal solution, because it is sufficiently difficult to install properly, involves a large structure, is not easily place-able while remaining accessible, and is not in the craftguide.
If you change the method of teleportation or add new ones, you should keep those ideas in mind.
However removing teleportation would be a really bad idea… it would make the game unplayable unless one would be willing to spend 30 min traveling down a mineshaft in order to get to the bottom and do some mining, then die, or if one survives, spend 30 min traveling up.
You could fall to get down faster, and run the risk of dying easily at the bottom, but if you survived, you would face the prospect of a large amount monotonous climbing.
on that note, here is a game design idea that may solve the teleportation issue.
separate the world into y-range-defined realms (you already have). Throughout each realm, have the mapgen spawn portals that lead to other realms, in a logical pattern. Have the portals be made of nodes, and have them activated by the mapgen. Breaking the structure de-activates the portal, and it cannot be re-activated. Players cannot activate portals themselves.
This would allow a gameplay that encourages x and z axis exploration to find the portals to go into other realms. Players can find, mark, protect, and map out paths that lead from one realm to the next, though they have to travel horizontally to get to the next portal to travel vertically. That breaks the monotony of climbing up and down ladders for tens of thousands of nodes with no change of scenery. also, if for some reason they break or lose a portal, they have to explore to find another.
An additional possibility is to have a unique portal type that *can* be crafted. It would be called a home-exit portal, and you would build it at your home. Then, when you want to teleport to your home from wherever you are, you build a home-entrance portal that takes you on a one-way trip you your home portal. Each player can only have 1 home-exit portal (building a new one removes the saved location of the old one), and entering any home-entrance portal bring you to you home-exit portal.
Another possibility is to have a server hub portal. The hub-exit portal is only build-able by the server owner, and only one can be made for the entire server. A hub-entrance portal is build-able by anyone, and can be activated by anyone. Entering any hub-entrance portal, teleports you to the hub-exit portal, but it is a 1 way trip. (of course the server owner should also place a home-entrance portal nearby, so people can get back home easily.) This allows the server to have a central area for players to meet new players and each other, and meet up to go on adventures together. The hub could have mailboxes for everyone, server bulletin boards, and eventually minigames for players to try a different game-mode.