I've been looking for this information. So thanks, and I have a bit to add. In my file Hanneman does not have his unique outfit in the Mage class (although the default looks similar at first glance). He's recruited as a mage, but the model doesn't show up until the class certification. Manuela has her unique as a Priest, but not as a Bishop.
If we are talking "canon classes", some characters come with classes already certified, although they don't have a unique outfit. Alois has Noble>Fighter>Brigand>Warrior and Shamir has Commoner>Fighter>Archer>Sniper all unlocked, although only the advanced classes use their unique models. Weirdly, Manuela, Hanneman, and the students I recruited don't have any Beginner Class unlocked, only the Intermediate Class they were recruited as. Although the Commoner/Noble class is there for each character.
EDIT: Just double checked and the students I recruited did have a Beginner class, but Hanneman and Manuela did not.