Jhulae, Gloombunny and WyzardWhately all make valid points. The only thing I'd like to add is that the 4e designers have already said they've removed the Profession Skill, and I think Craft too, so you "old master" concern is right out the window. The Skills rules are supposed to model stuff that heroic-fantasy adventurers are good at (picking locks, sneaking, etc.). It was never itended to allow you to "stat up" Leonardo da Vinci.
Trained vs. Untrained is a good way of modelling a lot of things, I think. You should really give it some more thought, and playtest it.