Thanks for the work compiling the skills like that, Reducer! It's very informative and really helps one get a grip on the skill system. And now that I have a grip, I find that I'm just a little frightened.
Apparently humanity lost more then we had ever previously guessed as being able to make leather is a secret that only the high ranking Tech-Priests now know. Sad.
What's worse is by going over this list, I've figured out how Chaos is able to maintain a hold in reality no matter what the Imperium dose. It's the food, the food! All agri-worlds are just busting to the brink with high level psykers or at least they're the only ones who know what's what on the farm. Hell, being a "farmer" is probably code for being a psyker because they are obviously the only ones who can learn that trade. Just don't ever mess with a farmer, they can all melt your mind with a weird look!
And did you ever wonder why the Tech-Priests are able to get away with so much without so much as a cross look from the Imperium? It's not because of some silly treaty that the Emperor him self made with them. We also know it's not because of some half imagined monopoly on tech that they like us to think they have even though just about everyone in the Imperium of any importance seems to be able to not only use tech but repair it and craft more tech items. No, the real reason is they control the MONEY! I mean, when was the last time you saw a merchant who actually made a living as a merchant who didn't have big metal tentacles coming out of his back? Ya, that's right, I'm on to the Adaptus Mechanicus and their conspiracy to control the universal market! First, they replace all the merchants so we're only buying Ad-Mech, next they'll take our leather... wait, ah crap!
I'm really wondering if the only determination for who got what trade skill was finding a career that had too few skills in a rank and tossing in some trade skills there to bring it up to code.