This part sounds cool - it probably wasn't part of the original Greyhawk (though I wouldn't know), but I really like the idea of Orcs and other traditionally "evil" ancestries traditionally having been the foot-soldiers of an evil power, but being fed up with it and setting out to do their own thing, which isn't necessary evil. It can serve as a great critical reflection on the notion of "evil races" and it can also be a really fun adventure element: "Yeah, there's a nation of orcs right next to the evil empire; actually, they were once part of the evil empire, but now, they hate it more than anything in the world. And they're looking to help liberate their orc sisters and brothers there ..."