A way I thought was to take advantage of the fact they are full columns. They connect both the floor and the roof of the caverns. As such, one can channel the columns, assuming there is room in the level above the roof. Another method is to build up/down staircases and then carefully designating (from the top down) for everything to be removed/channeled.
However these methods have different chances of success, and in the most part will result in cave-ins. Mining the columns at floor level is a decent compromise, as long as one understands cave-ins. Unless someone disables them in the configuration files, cave-ins happen when a wall or floor tile loses connection to any adjacent orthogonal element. Dwarves, however, can move in all directions, and so some care should be used when mining columns to prevent mining the floor above the cavern level.
Another method is more effective, although it requires a new world (meaning this has to be thought of at start). Adjusting, in Advanced World Generation, the Cavern Layout Parameters, namely, setting Openness at 100 and Density at 0, will try to create highly open caverns.
There is yet another method, albeit more hackish. Assuming you have DFHack r3 installed, you can use the tiletypes command to selectively delete the stone columns, although it does require a considerable amount of work.
- Open Dwarf Fortress and while in Pause, go to the offending cavern.
- From the top down, designate any freestanding column (without an orthogonal connection to the caverns' walls) for mining. Do this for every level where there are columns.
Type the following within tiletypes:
- filter d 1
- paint sh floor
- paint h 0
- range x y z
The first command should filter only the wall tiles you selected for digging, the second signals for them to be replaced with floor tiles and the third signals that they should be visible. You can input whatever range you want, although it might be handy if you set a high value for x and y. tiletypes works with the k (Look). Place it in the lower upper left vertex of the "cube".
- Press Enter and the designated tiles should become floor. Unpause and a collapse warning (along with a good amount of deathly dust) will appear.