Maybe this idea have been posted in other forums, I hope not so everything that i will write from here will be in vain.
The professions will become available once you reach a certain level of one or more proficiences. Maybe it can be a skill that appears in a golden colour or something that difference it from normal skills. Only one profession can be learned per character.
Professions will make the need of being in a settlement even bigger than now. But its something logical, one lone person cant expect to achieve the same things than a group.
A character with a profession will have bigger bonus when grinding purity in the things that are related to it. For example, a cooker will have higher bonus of purity when he cooks. Characters without a profession will have a purity limit, and the ones with one will have a purity limit for things that are out of his area of expertise.
Maybe when you get a profession you will get some skills only available to the profession you choose. For example, if you are a lumberman you could get a skill that increases the speed of chopping trees; and another one that gives you thechange to obtain certain inspirationals that cant be obtained by other way.
The ones that I have thinked of are the next:
Miner: Will mine faster and will be the only one that can get different ores when doing it.
Lumberman: Will chop trees faster and will be the only one able to distinct some kinds of trees and get their special wood.
Cooker: Will have almost no chances of getting his food burned when cooking and will have access to some unique recipes.
Well, I hope you like my idea and I want to apollogize for my english.