@Dame: Well, ok, don't rule it out. But I'd like to see migrants make a bit more sense anyway. Although, the fish cleaner who really wants to be a metalsmith showing up to a map without water? That kinda makes sense.
"See, I was trained as a fish cleaner, but since you don't need any of those...how about I go work in the forge? Eh? Eh?"
As for dwarves going off and giving themselves jobs...I'd like to see some material prioritization in place before that happens. I mean, let's say I've got a Baron who LOVES nickle items. And I can't mine for nickle, so the only nickle I've got is the two bars I traded for. I'm going to be royally ticked if some stupid fish dissector with dreams of metalcrafting comes by and turns that nickle into a toy boat on his own.
Let's see, how best to handle that? Maybe have them put in a request with the manager? You'd get lists of requested jobs by different dwarves, and you could approve or deny them based on the situation. So, if an aspiring mason wants to make a felsite throne and I've got tons of felsite...go ahead. But an aspiring weaponsmith wants to use my only steel bar to make a spear? Uh, no, let's leave that for the legendary weaponsmith, thanks.
It could even be automated, where the manager only approves requests that use common items, or maybe tasks that are already on the approved list.
Which gives me a new thought. How about in the manager screen, being able to select a minimum/maximum skill level per job? Say, I don't want any dabbling armorsmiths making steel plate mail, but they're welcome to churn out bronze caps. That would help a lot when you've got multiple crafters in a large fort anyway. I frequently have to micromanage my forges to keep the jobs I care about in the high-level forges, while letting the baser tasks go to the training forges. I want to train up my other weaponsmiths, so they can make bolts or whatever, but I prefer to let my highly skilled smiths make the real weapons and armor. Or, say, restrict my bed making jobs to my legendary carpenter but let the apprentices churn out bins where quality really doesn't matter.