Alright, let's get the difficulty thing out of the way.
The basic skills needed for a dwarf fort would be:
Mining, Masonry, Carpentry, Farming and Brewing. Yes?
-Mining: Mining requires a basic sense of Geology and architecture, so it can be a basic skill in that regard. What if mining is the base skill of dwarves as a race, all dwarves know something about mining(and arguably are all novice miners) due to geology knowledge being an important part of the dwarves common knowledge-set?
-Masonry: Masonry at it's most simple needs knowledge of materials. However, the lack of knowledge of materials would result in destruction of the material, and is thus prefered to be abstracted away. Let's assume that a random idiot would be able to make simple things like tables and chairs, but perhaps not how to make a floor grate.
-Carpentry: Would need knowledge of materials, again that is abstracted. I can see a random idiot being able to make a bed, but not so much a barrel with would need to be water-proof. Unfortunatly, barrels are quite important in DF.
-Farming: Anyone can throw some seeds onto the floor and hope they'll grow. In a more detailed farming system the thing that seperates the boys from the men would be knowing what conditions are needed to make a plant grow and being able to inform the player of these instructions. In the meantime however your first year would be able to sustain of a plumphelmet farm that doesn't do so well in the second year for 'mysterious' reasons.
-Brewing: As the chemics knowledge required is quite refined and it's a part of dwarven culture, I would suggest that this should be and inherit skill of the dwarves.
For more specialisized skills.
-Butchering, shouldn't be to hard to do though dwarves who are a bit meek should probly be hestiant and have the animal in question escape a lot. The skill lies mostly in identifying the parts and preserving the meat. So... bad quality meat will go off quicker and a bad butcher won't be able to get as much meat from a cow as a good butcher would.
-Cooking. How many people can't bake an egg here? Cooking is probly taught by parents to their children. Some exotic product might need a difficulty modifier for either being unknown to the specific civilisation or for being hard to handle(baking an egg is easy, baking a salmon just right isn't)
-Tanning: This skill requires knowledge, an perhaps products of a bad tanner would go off more quicker or the tanning proffesion can't be assigned at all unless the dwarf in question has some skill in it.
-Weaving, learning how to weave is simple. The result's not very pretty, but it's simple. However, making a loom should be quite difficult.
-Dying: is at heart a simple skill, and simple to make a workshop for. Result wouldn't be too pretty, but hey.
-Clothesmaking, this ones a bit weird. While clothes making would require basic knowledge of measurements, you could argue it was very common in medieval times and most people(women) knew their way around a piece of cloth. You could again say it might be an inherit skill for adults but on the other hand you could throw in some flavour and say it's a speciality of the humans or something. (Most forts can do without clothing industry for a while anyway)
-Leatherworking, I'm going to say that leatherworking has the same issues as clothesmaking, but then combined with some of the specialised products of leatherworking(Waterskins, though leather).
-Crafting and gemcutting: I'm going to say this would most require knowledge of material(but knowledge of material is abstracted). Perhaps gemcutting would need some mathematical knowledge, and some of the crafting skills would need knowledge, but otherwise it can go under the old system. Though, I'm not to certain about the yeweler's workshop.
-Bowyering: Sure it's easy to put a string on a stick, but better bows actually require combining layers of wood that vary in flexibillity. Perhaps bad bows break quickly?
-Siege engineering: To be honest, I really wouldn't know how to make any kind of siege-engine without an example.
-Taming/Training, would require a specific trainer to know enough about the animal so they can train it succesfully. But I guess that's what the pet-exotic tag's for.
-Glassmaking: Would require knowledge about glass and ovens.
-Mechanisms: Would require mathemathics.
-Soap making: Would require knowledge about making soap. I dunno about the medieval production, but I think the production can be quite dangerous?
-Blacksmithing: requires material knowledge, is abstracted. Probly the same as masonry and carpentry. Can make basic stuff easily.
-Weapon-smithing and Armour makng: Again, material knowledge, whichis abstracted. I think bad quality equipment shouldn't last long.
-Strandextracting: I dunno anything about extracting adamantine from it's ore, so I can't say anything. You guys?
-Woodburning, potashmaking, lye making and pearlashing would probly require the exact instructions how to do it. I don't know much about this either TBH.
-Milling shouln't be too hard, because the machine does most of the work. However, how many of you know how to maintain a mill?
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New jobs:
Pottery: Shouldn't be hard, but glazing might be a bit more difficult. So no water-tight pottery.
Beekeeping: Needs knowledge about how to catch a swarm, how to properly get to a 'tame' swarm and how to force a swarm to split up.
Feel free to correct me. I think that it would be better for the gameplay if certain skills are inherit to a race if it's vital for their survival(brewing). Perhaps also skills that are tied to a culture rather then a race(So one dwarven civ that's good at leatherworking and another dwarven civ that's good at siege engineering. It could make for a nice bit of difference between playing different civs)