Setting up a hauling system
isn't supposed to be a free or easy task - that's the value it has. Players here laud the challenge in this and other games.
Further, I believe that if you are actually
forced to clean up the rubble before you can continue mining, and leaving trash strewn about has in-game consequences (not counting the meta-game consequences of FPS loss to a bloated vector), then it may cause the reaction in players to actually start working on cleaning up their trash.
There already are suggestions on how to deal with trash items, from dumping them "off-map", to consolidating "amalgam" walls that delete all items in the compacted trash walls, to the old stand-bys of just atom-smashing or magma-dumping everything.
More realistic suggestions include composting items (which would be more important when we have farming changes) or incinerating them, as well as the aforementioned "just make a solid wall of rubble at the entrance to the mine like an anthill". So long as they consolidate/compact into walls that delete the items, and there is an in-game incentive to eliminate them (your mining cannot continue until you clear the workplace), then you side-step the FPS drag problem.
I actually see that as a positive, not a negative. It makes the game "harder", so to speak, as the game goes on without the player actively having to micromanage the rubble. First tiles you strike into the earth? You only have to haul rubble a couple tiles away. Digging straight for the magma sea to try to set up a magma forge early? You're going to have to haul that stone up 100+ z-levels to find the dump site. When you are just starting out, it's easy, but the larger and more ambitious your mining becomes, the more you have to negotiate the logistics problem.
Further, it's a very serious problem that stone is a "free" resource in this game, in the sense that we always have limitless supplies of it on hand to accomplish any task we can use stone to fulfill. Most city-building or strategy games derive their challenge from the fact that resources are meant to be
scarce. Almost all resources in DF besides maybe wood and iron, depending on embark, are available in such huge quantities that you never need to worry about scarcity, and indeed, the problem is
overabundance of resources. We don't worry about how we are going to feed our dwarves, we worry about how to get rid of the excess food. We don't worry about if we will have enough stone to supply all the walls, mechanisms, doors, tables, chairs, etc. we need for defense and infrastructure, we start building walls and roads to just eliminate excess stone.
I wrote a pretty massive thread on farming specifically about how we need to make organic resources more scarce and something that can either be available with scarcity if you put little effort into it, or can be available in greater degrees of abundance for greater degrees of effort and understanding of the system, but we need the same thing for inorganic resources, as well. We need to make mining slow enough and hard enough to give workable stone actual
value to a dwarf.
There's something very wrong with the notion of a game about dwarves that see stone and even gems and precious metals like gold as nothing but trash that they need to get rid of for their excess.
In fact, I'd actually like to see stone become less useful overall - clay and ceramics were added to the game, but are nearly useless because clay doesn't do anything the excessive stone you are trying to find ways to get rid of isn't already capable of doing. Glass doesn't fare much better.
We have come to accept and even enjoy elements of the game that don't give us a "benefit", like dwarves needing to sleep and have bedrooms, and incorporate it into our game, and we enjoy the need to solve these problems the game forces upon us.
The fact that stone and ores and gems are going to be in the landscape isn't going to change, and without making caverns even crazier, the only real changes to them will be the 3d ore veins. If we are to impose a scarcity of stone, it must be through making the act of mining itself more slow.
Only then can we have the benefit of the challenge of trying to make a temporary shelter for our dwarves while the slow process of excavating the "true fortress" takes place. Initial constructed wooden or stone shacks might get buried in rubble amalgam walls, and become "underground" as the fortress below expands. (Of course, hopefully, this goes hand-in-hand with the conservation of soil, and end of limitless sand and clay from floors, as well...)
For those who make megaprojects, do you know how the ancient Egyptians made their giant temples and obelisks in an age without cranes and powered machinery? They used sand. They carved the obelisk out of one giant piece of stone at the quarry, floated it whole down the Nile on a barge, built a sand ramp to get it up above the podium, and then dug the sand out from under it until it was sitting right-side-up on the podium. They engraved the columns of their giant temples by piling sand up to the top as a scaffold, and then digging their way down as they completed their engravings...
Making a pyramid in Minecraft Creative Mode is easy.
What the Egyptians did was impressive not just for lasting so long, but for what they accomplished in spite of their limitations.
Likewise,
Wieliczka's cathedral is impressive because it was mined out using "realistic" physics models where you had to actually remove the stuff you excavated. No speedy stone vaporizations for them.