You might want to check out the Dragonstar RPG by Fantasy Flight Games. In that universe, Dragons rule everything, too. You might get some interesting thoughts on how dragon rulership impacts things.

You might also want to check out the old Dark Sun box set for thoughts about handling multiple characters. It addresses some issues you might not have considered, like how fast the inactive characters level up.

You might want to consider adding some classes to replace the ones you're disallowing, since you'll be denying players who enjoy those classes their favorite options. Maybe allow the warlock or a war mage instead of a wizard. The Midnight RPG had a monk-like character who didn't have anything to do with a monastery.

Lloyd Brown