Mecheon
Sacabambaspis
Greyhawk is absolutely a kitchen sink per word of its creator. Its the setting that practically introduced the "Hey here's this place that a whole new group of elves with a unique stat block have been living" in the Valley Elves. Its the setting that has a whole published and popular adventure that's about an alien spacecraft crashing. Its the setting that has portals all over the shop. Heck, OD&D had a Barsoom encounter list hidden in one of the books, or at least a "Planetary (Barsoom, etc)" oneSo, Greyhawk is a kitchen sink then? Everything released should be there?
Dragonborn are the easiest thing to do. Just grab that mysterious western empire of dragon lords, pry it away from "Some obscure French comic with no D&D connection" that its currently tied to, and go "Yeah it had dragonborn all this time, who'd have thought it". Its not like its ever been published as anything other than "Mysterious and to the west" in official stuff anyway