Yeah. Difficulty of the task should be reflected in the skill check and quality systems, instead of out right preventing the task. Because in theory you could learn anything by experimentation. Someone had to come up with the idea in the first place, so unless the dwarf has a lazy and/or uncreative personality, they should be able to try to perform the task from common knowledge.
Of course some failures, like the aforementioned herbalism, could have catastrophic results. Actually any below skill attempt would be more prone to accidents, so maybe have no successes on Kohaku's skill check idea inflict some kind of injury, severity and target depending on the task performed. For example, most carpentry jobs would damage finger, hands, and the such, but a critical fail herbalism would poison the herbalist. Or Critical failure on architecture make for a bridge that collapses the moment weight is put on it. though in most production jobs, a critical failure shouldn't waste resources. Just because you hit your hand instead of thee sword you're forging, doesn't mean the sword-to-be is ruined.
Also some jobs could use some synergy. Historically smithing was more divided on metal type than on object being made. A blacksmith(iron) could make horseshoes, nail, farming tools, and weapons and armor. Sure, just because their a master nail-maker doesn't mean they're also a master sword-maker, but being a master at making nails should impart more understanding into how to make a sword, due to better understanding of the forging process and the qualities of the metal. Also if a task centric difficult goes into play, we need nails to train our blacksmiths with.