I considered armor for the dragon, but armoring exotic creatures is difficult and expensive. You're paying way more for any armor you try to get than the fighter is. The humanoid fighter can drop 1,500 on a set of full plate and then consider getting it enchanted with the rest of his cash. The dragon is paying double that, or quadruple if they're large. They wanna dress up in mithril? They better be willing to pay through the nose for just a mundane set.