I dunno, I prefer a crazy duplicated wizard putting random stuff in dungeons over Elminster...
Yeah, but that makes Zagyg actually the Oerth-version of Halastar Blackcloak. The Ruins of Castle Greyhawk are also known as Undermountain.
Other thoughts;
The arc where elves show up and take over the Isles of Lendore could be replaced with an Evermeet take-over of the Moonshae Isles.
The Tiger, Wolf and Bear Nomads could exist in the Hordelands, with some bleed-over into the berserker-lodges of Rasheman, with the Rashemi witches being the remains of the Bakluni civilization (which seems vaguely Persian, with lots of genies and stuff, which blends acceptably with the Rashemi elemental focus).
The Suel / Bakluni war, with the Invoked Devastatation and Rain of Colorless Fire, would be a battle between the caliphates of the Bakluni, which has degenerated into Mulhurand, Thay, Rasheman and Aglarond (and Calimshan, formed from people who fled far from traditional Bakluni lands, fearing that the Invoked Devastation would continue), and the empire of the Suel, which was far more effectively destroyed by the Rain of Colorless Fire (which created the lifeless waste of Anauroch), and whose people are now the paler-skinned inhabitants of Cormyr, the Dales, the Moonsea, the North, Waterdeep, etc. Countries like Amn, Tethyr, Damara, Impiltur, etc. tend to be of mixed blood, with darker Bakluni having interbred for thousands of years with paler Sueloise.
The only 'pure' Sueloise culture left is in Halrua, Nimbral and other enclaves that survived the war. As the Scarlet Brotherhood is now based in Thay, which, according to the tweaked mash-up timeline, is of Bakluni heritage, any racism among the Scarlet Brothers is based around the superiority of the *darker* man, and particularly focused towards the pale-skinned, fair-haired humans of obvious Suel blood. The Brotherhood is still supremacist in nature, just with the colorations reversed. The 'aryan' Suel are considered 'half-bloods,' said to have thinned their blood with that of elves, in Thay. (In other nations descended from the Bakluni, citizens with Sueloise colorations are not unknown and predjudice is a rarer thing. Mulhurand, Rasheman and Unther tend towards darker complections, Aglarond and Chessenta tend to be more racially mixed.)
In Oerth, the Scarlet Brotherhood keeps slaves, generally from Hepmonaland, which wouldn't be 'doable' here, since Hepmonaland would be Chult, which is ridiculously far away from Thay. So instead, their slaves tend to come from the Tiger, Wolf and Bear nomads of the Hordelands. Of course, just as Oerths racist Scarlet Brotherhood enslave fellow Suel from Hepmonaland, so do the racist Bakluni/Thayvian Scarlet Brotherhood here enslave fellow Bakluni-descended barbarians from the neighboring hordelands. Evil doesn't stop to worry about such trifling ironies.
As a result of ancient hatreds, Thay and Halrua, the two most magically potent nations on the continent, expend quite a bit of resources spying on each other and plotting against one another.
Cormyr fits well as the Veluna of this setting. Both tend to be the 'average fantasy nation' of their settings.