Caught between Miazaki's two loves:  flying machines/war machines and magic/folklore creatures.  That describes Sanji to the letter, especially since there is a cooking scene when Sophie first comes to the moving castle where Howl helps her fry up bacon and eggs and boil some tea.  And of course, Sanji has "Howl's hair turning orange." worthy freak outs on a regular basis.  My only question is what the name of his fire demon would be as Calcifer is already taken.