Accidentally posted before I was done... Oops!
Nami is a Maid of Light — not too too sure about this one but it's what I eventually decided upon.
Usopp is a Page of Doom, because, like... c'mon. I just think that's perfect for him. He's fundamentally lacking rules and discipline and throughout the story he'll (presumably) become a brave warrior worthy of his aspect.
Sanji is a Mage of Heart. Not only does he suffer from Oda's obnoxious gags surrounding his love of women, but from the innate emotional tampering attempted by his father before his birth. He knows a lot about love and what it means to feel things, and it causes him no small amount of pain to do so.
Tony Tony Chopper is a Sylph of Life. I didn't think about this one too much, it just felt right.
Nico Robin is a Seer of Void. The Void aspect is pretty obvious given her connection to the Void Century, and her struggle with her knowledge and how to apply it given her persecution led me to the Seer class. I guess I could be convinced of Mage, but eh...
Franky is a Witch of Mind. He actively uses his knowledge of mechanics and the logic of engineering and then throws that all out the window to make goofy, silly gadgets. Perfect.
Brook is a Prince of Doom. In this, I am more referring to the idea that he is one who destroys Doom rather than one who destroys with Doom (although he does, in fact, do that). He actively breaks the laws of nature by existing and he constantly rebels against prevailing ideas about what rules are and what someone ought to do.
Jinbe is a Knight of Space, because they needed a Space player and I don't remember a lot about Jinbe. He just seems like the Knight type, I guess.