Just FYI, most of these can be modded. (Incidentally, I am planning to do most of them when I understand plants a bit more in the new version and things have settled down.) I'm not saying that's a reason for Toady not to consider them. Just letting you know that you don't have to wait around for all of these necessarily. Anyway:
(1) Preservation at the very least should definitely be in the default game.
(6) Also absolutely occasionally diseased water should be in the default game. This is actually much easier than a food rework - Toady would just had to add some extra types of contaminants to natural water bodies with procedurally generated syndromes. Which he already has coded for weird rain in terrifying biomes, and he also has contaminants coded in water (mud, salt, etc.). However, it is a myth that nobody drank water in the middle ages, or that doing so is just always dangerous or whatever. People who could afford it would drink beer more often, but it was simply too expensive for everybody to. It would probably be most realistic to have coin flips for which water sources in game are considered contaminated, with higher likelihoods for downstream and for standing water. Possibly ALSO a coin flip for every drink. So for instance, something like "Stangant water = 100% contaminated. Brooks = 25%, rivers 75%. Aquifers can still pass salt and maybe toxins or even viruses depending on how porous the rock is, so maybe 20%? Whatever, something like that. Then also like 1-2% per drink on top of that (sometimes a random animal dies or something upstream now and then). This would model reality pretty well, with poor desperate people able to get by, but it being best to have preservable drinks, and some areas simply being contaminated, period.
(5) Yes, it should require water as an ingredient. Really most things in the game should require water... though if so there would need to be a much better system in place for making water reactions way less annoying. How about: either a bucket of water in the reaction OR you can build it over a water source and not need it, just like magma forges work?
(4) Yeah probably would be nice. This one is completely trivial to modify yourself, though. Just go into the "plants_standard" and "plants_garden" etc. raws and find the "alcohol" material definitions, which will include the name of the booze. You can just write in whatever else you want, and have your turnip vodka and whatnot.
Random other comments:
-- Hops are not just for flavor, or even mainly for flavor. They were originally used for their strong preservative qualities, considering that "small beer" was only a couple of percent alcohol at most, which wasn't enough to guarantee clean long term storable drink by itself. 1-2% alcohol + hops is much more stable. Wines and spirits would not require these additional preservatives.
--Stills seem like they should require fuel as well, at least for some things, maybe all (possibly even magma stills as an option. Seriously). Even for just beers, you generally boil the wort prior to actually beginning fermentation, whether wild or cultured yeast are used, at least in modern times. And definitely, of course, distilled things. For wine and for medieval beer, I don't know if they actually boiled prior to fermenting or not. Might be worth looking up.