The Middle Distance

I would really, really HATE Mark Sheppard playing GO!Crowley. Immeasurably. They're such totally different characters to me; they don't look alike or think alike or have similar motivations or...anything, really. (They're not even pronounced the same way.)

True, but so much of the story takes place in London, which is very diverse. I've seen the idea of Crowley being played by a non-white actor go both ways in people's opinions. I tend to agree with you: he is really the hero and protagonist of the book, and we do sympathize and empathize with him thoroughly most of the time. I think it's OK for Crowley not to be white, as long as the far more actually demonic Hastur and Ligur are. But then, keeping all the supernatural beings white-looking makes a kind of sense too, since they're actually all sort of wearing human "costumes" and not their true forms. Maybe if they're all white, they would actually appear less truly human than the much more diverse cast of actual humans. None of them actually have a race or ethnicity in human terms at all!

Wensleydale or Brian or both could be PoCs too. I'd say Pepper and Adam, except that they're described as having red and blond hair respectively. (And of course a PoC Antichrist would take us back to the offensiveness issue, even though he's not in any way actually evil.) Anathema could certainly be mixed-race, and Newt as well.