Created for thread: http://www.bay12forums.com/smf/index.php?topic=126714.0
Pre-embark story and information: http://www.bay12forums.com/smf/index.php?topic=126714.msg4294434#msg4294434

Think you can survive without stone? A joyous wilds shrubland/joyous wilds savanna/untamed wilds mountain embark where all stone except metallic ore is replaced by different, varied types of soil that change as you go deeper in z-levels. Unlike my previous attempt, here the floors have changed into soil too and grow cave flora normally. Things that DF absolutely requires are made of non-soil materials are made of gravel, a worthless and useless non-stone material. Civilizations, including your own, and other embark sites have access to stone, which also behaves normally if you can acquire it. Any mods can probably be added so long as the inorganic_stone_soil.txt file is preserved.

Steps to recreate:
0. Delete all unwanted non-layer stones or reassign them to hell
1. Generate a world where every layer stone is not IS_STONE and is SOIL instead
2. Manually dfhack changelayer these stone-soil types into types of actual soil
Doing it this way should and seems to allow dfhack to change the floor as well. It says so in a very roundabout way in the documentation. Once I figured that out...

3. Manually change every stone that was changed into SOIL into IS_STONE, finalizing the above change and making any stone you can obtain from traders usable.

4. Create a dump type of non-stone non-soil material for next step that is neither SOIL nor IS_STONE. Mine is a worthless brown-gray and grainy material called simply "gravel" to reflect its infertility. Some features (pebbles, boulders, upward and downward passages, and apparently the floor of some [mountain?] topsoil layers) require that a non-soil type exists as a layer on the map and there is no easy way to remove this - for example simply painting over boulders is not sufficient and will lead to bugged material appearing in places on the map. This will be the only thing on the map that does not grow flora and can be engraved, other than the ores. Since it's neither soil nor stone, it's otherwise useless.

5. There will be flashing boulders on the surface. Target one with dfhack and change layer with force to change these into the dump type. The floor of one of the topmost levels as well as any features that must be made out of non-soil now instantly become the dump type. This will change the walls of that layer into the bottom-most soil type on the map, and they can't be changed with dfhack anymore (in the case of this map it creates a layer of "fire clay" that is actually gravel). To fix that, make everything else not be IS_STONE and make a copy of the dump material that is IS_STONE. I recommend replacing SILICEOUS_OOZE. Paint over the offending walls with tiletypes (p mat: stone special: normal), then reverse the previous changes. This is a little painful but the only way I could think of. Easiest way is to autodesignate it with diglx and use that as tiletypes filter (f designated 1). If you named it "gravel", this magical gravel used to make the walls now drops "gravel" when mined. To make this not happen, make it a vaporstone (sugg: [MATERIAL_VALUE:0][STATE_COLOR:GAS:GRAY][SPEC_HEAT:1][BOILING_POINT:10001]). This won't cause issues with traders if it has no material value (and civilizations don't have access to it anyway, if you used SILICEOUS_OOZE).

Congrats! There is now no usable stone on the map except in ore veins, yet everyone else has normal access to stone. The only way to tell it was modded and then hacked (other than everything) is the dump material.