I'm sticking to my idea of the Prince of Galam, being a different kind of HERO type that uses magic/staff instead of swords, he joins at level 8 and joins as you escape Granseal. Feeling guilty for what happened to your kingdom, vows to help rebuild and defend it while trying to find a way to save his father with research into the devils. He will act like a mini adviser until Astral joins, after that he's just almost like an apprentice of Astral. Also, he falls in love with Elis, not Bowie, which means you can add a relationship system now, you're welcome.
Other than that, I'd add a centuar mage, because why not?