Well, the evil stuff is the leading point of the poll, so I guess people want it, square or not-square.
I have also read up a bit on chemistry, and I must say that it will get quite difficult to port a system based on RL into DF, which can be easily understood and serves an ingame purpose.
For example to make Ultramarine dye, you need: Kaolinite, Sulfuric Acid, Sulfur, Charcoal, Ammonia, Carbonic Acid, Lye... that is mixed in the chemist. Then pressed into cakes, in the screw press. Then dried in a kiln. Then grinded into dye-powder in the quern/millstone. So yeah... I think people just grind 1 plump-helmet instead. Or buy dye(10) from any caravan.
Or making industrial cyanide. You need a platinum-coated catalyst, Oxygen, Ammonia, Methan... and with that you can smelt ore without fuel. Again I'd say that people would rather use fuel/magma.
There area few things I find interesting, especially early chemistry, Salts, Oils and Spirits, used for acids, poisons and more ways for things to go boom!, but I might have to add a few more inorganic mats. Higher drop-rates for Realgar, Cinnabar and Rocksalt, replacing Kimberlite with Apatite, Opriment or Vanadenite... or mineable guano deposits, bat-guano comes to mind.
I have much more here, but I try to keep it understandable. Its also a but hard because some things have medieval names, while others only have modern names. Oil of Vitriol is Sulfuric Acid, or Aqua Vitae is Ethanol... I probably stick to the old names, but I might have to invent a few for the newer stuff, like
Methan or Thermite.