Just a note here to say that I don't believe
anybody thinks that implementing any of these alternate beverages would require a new
labor. Picking & drying tea leaves would fall into the Threshing labor, grinding dry coffee beans would be done by a Miller*, etc. While it's true that actually
preparing hot tea/coffee would technically be a Cooking action, I think this should be a special case where individual dwarves don't
need to have Cooking enabled if they're preparing the drink in their own quarters.
* Querns & Millstones used for grinding coffee should impose a negative quality modifier on the next few batches of flour created in that same quern/millstone, and vice versa.(Although I
do believe that Brewing, Vinting, and Distilling should be broken into three separate labors, as they're 3 different processes with very different chemistries.)
Human works well enough with no drink, a tot of rum might help fortify them slightly
Mmmm . . . for humans, drink (certainly at only 1 drink per day) doesn't do much to "fortify", and only functions as a
morale booster more than any other positive effects. In fact, that could be very much the same for dwarves: The observed symptoms of sobriety might not be due to actual physical withdrawal, but instead be purely
psychological in nature: They know that they're laboring for an overseer/mayor/monarch who doesn't think they're
worth the effort of providing liquor for, and it's very demoralizing to be denied your well-earned drop of liquid happiness. So, understandably, their work ethic plummets. (That
wouldn't explain their slower reflexes, though.) Attributing their lethargy to
ennui makes a lot more sense than making up some weird-ass dwarven biochemical needs.
A dwarf has a scale that is almost up against "the maximum alcohol anyone could physically drink"
Almost to the maximum, indeed. Dwarves can still drink themselves to death, and of course the upper limit is defined by
gnomes. (Gnomes currently can drink
infinite amounts of booze, but IMO they should definitely have some sort of hard limit on consumption, like 100% of their normal body size.)