To be more on topic, I will debate some of the OP's suggestions. Sorry, but you asked for people from the other side
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Wood Burning should be separate. I do plenty of wood burning, I don't see how else you can get fuel reliably (once you run out of lignite and bit. coal, of course). Potash and Lye making are similar enough.
Milling is constantly used, and should be separated from Threshing. Pressing I assume will become much more important later, so this combination is likely a problem.
Animal Processing is blowing my mind. Sometimes I need that control, especially with Milking and Cheese Making. Quality isn't everything when you have more animals then milkers. Shearing and Spinning are not realistic to combine, and Beekeeping makes no sense in there.
So basically, I would merge Potash and Lye, and wouldn't really care about Pressing and Threshing. The rest, I find too much use for to lose. Remember that skill synergy would help with your "farmers can't do other tasks" argument, and to be honest most people were farmers at that time.
For the additional ones:
Fish Dissector - Support, or merge with Small Animal Dissection (there isn't much use of that)
Siege - Oppose, as they are completely different.
Pump Operating - Really, it can be its own skill. I have no problems with it.
Small Animal Dissection - Neutral. I really think it should be separate, but it wouldn't be that useful to me.