Awesome! I’ve never really messed around with Greyhawk, except in the incredibly vague sense that at some point I played 3.5e and didn’t mess around with its setting assumptions too much. I’m really interested to dive a bit deeper into it with 5.24. The way you pitch it sounds very familiar to exactly what appealed to me about my own favorite setting, Nentir Vale.
The one point here that is not so appealing to me is this idea of “muscular neutrality.” I’ve always found the whole “balance must be maintained, too much good could be just as bad as too much evil” thing a bit… I don’t know, silly? It’s one thing to have villains who represent traditionally “good” ideals pushed to an evil extreme, but actually having the ascendancy of good be some sort of existential threat due to “imbalance” just doesn’t work for me. Fortunately, it sounds like the setting is flexible enough that this theme can be safely ignored. Though in my understanding there are some fairly prominent “muscular neutral” characters in the setting, such as Mordenkainen. I wonder about maybe including them, but portraying them as misguided - having the need for balance being a belief they hold rather than truly being important for the wellbeing of the cosmos.