So this would be the third possible campaign setting for my mostly-but-not-quite nonexistent game. I began thinking up this campaign setting during the few sessions I had with the group out of Rock Hill and it slowly developed over a few game sessions.
The foundation of the setting would be Greyhawk during a mashed-up version of the Greyhawk Wars. There isn't a whole lot fleshed out for this setting, I would mine modules and supplements for concrete material, like dungeons, NPCs, cities, etc.
The meat of my creative input into this setting would be rooted in my interest in history, especially the history of warfare. This setting would be a sort of total war scenario, where Geoff is occupied like the "Against The Giants" silver anniversary supplement, Iuz and his machinations, a resurgent Temple of Elemental Evil, various demi-humans in the Pomarj, etc. (I'm extremely poorly versed in Greyhawk, so I am sure I am screwing up the details and I know these events are not concurrent by the book.)
The backdrop of the campaign would be heavily tied into wars. The initial group would be in the county of Gran March in the recently liberated city of Hochoch (this according to Against the Giants). From there, the setting could involve the PCs adventuring in occupied Geoff or through war-torn counties like Gran March, Yeomancy, and Sterich. The sandbox would be full with intrigue, conflict, opportunity, multiple sides, and plenty of enemies and allies on both sides of the war to fill the sandbox.
This setting appeals to my sensibilities by creating fictional military campaigns for the ongoing wars in Geoff. By using published material, prep work would be reduced since I can fit pieces in as needed. For example, the homestead under siege by goblins from B10 could easily fit into this setting, along with the myriad of dungeons, lairs, and fortresses littered through the B series, the G series, and pretty much anything and everything Mystara and Greyhawk.
This game would run more like a typical fantasy setting. There wouldn't be any apocalypse to survive and adapt to nor a "historical" setting meshing with fantasy. Typical might be the wrong word, more like "familiar." So would players rather have a "familiar" sandbox to play in, or would the fun in discovering an unfamiliar setting provide fun? Would it not really matter if the DM and players were any "good"?
Well, it's a third idea to throw in the hat.