(when) will we ever get some (pseudo-)chemical interactions going on? Like in the simplest sense, things decaying/fusing into different things under certain conditions? For example a lot of things would release toxic fumes when heated or burned, requiring ventilation systems (for carbon monoxide, among other things), some other things might react violently to water (like calcium oxide) or acid (once we get more than one kind). Some might react violently to heat or shock, producing blastwaves(releasing lots of compressed gas and heat in a very short time) of various strength. I'm thinking both of constructive (masonry, hygiene) and destructive (exploding minecarts, yay!) applications for this.
Another thing - how about allowing the player to call for austerity measures in fortress mode, or even martial law, where food and booze would be rationed to sustain the fortress for a longer time, during a long siege for example. I know this can be done manually by walling off parts of the food stockpile, but it would be easier just to tell the dwarves not to eat and drink until they're really hungry and unhappy. Also, this might have positive settings, for when the fortress is doing really well, making dwarves eat better and more often, making them happier.
edit:
Sent it to Toady the proper way. Leaving it here in case someone has an opinion on this.