Wow. I must admit, I this was a hoax unil I realised that I'd never tested DFHack's mode set command in arena mode and curiosity overtook me. A quick test proves this to be true; upon reloading the map you will find yourself in a flat hill biome with a couple of murky pools and flashing ' and ` tiles (reminiscent of grass on fire) which seem to cycle between all the different materials defined in the raws. However I would like to point out that some of the materials mentioned, along with their respective syndromes, are most likely due to mods-for example, I seem to remember Masterwork including the "flash of blinding light" material to make reactions more lively. Also interesting is the fact that the whole map is made up of only 2 z-levels; the ground's level and the one under it, without any above.
(http://i.imgur.com/7wI7Zyc.png)
(http://i.imgur.com/IfB8zBv.png)