I'm against arbitrary changes to the source material.
You want to do Iron Man's origin in the Middle East? Absolutely, it makes perfect sense. That's where the modern war conflicts are.
You want to make Tony Stark black for the sake of inclusion and to reflect the black experience, well there are better ways to do that. You can add to the mythos with new black heroes like War Machine and Riri Williams. These are new heroes who add to the mythos instead of shifting it. They have their own black identities, origins, experiences. To give those backgrounds to Tony Stark you would have to change Tony Stark.
Miles Morales is a good example of how you can make a black Spider-man without making Peter Parker black. By making Peter Parker black you lose Miles Morales two parent home which black kids need to see, you lose his cop father which black kids need to explore, you lose his Brooklyn connection, you lose his new super powers, you lose his relationship with Peter Parker, you lose the permanent co-existence of the two Spider-men (since Peter Parker will go back to being white), you lose all the things that make Miles special and replace that with another Peter Parker story but with black skin.
If you truly want a Spider-man or Superman story that speaks to black people you need to make alot more changes than just pigmentation and if you're going to make those major changes then you might as well create a new character. You don't lose anything. You add to the mythos.
Miles Morales will be around forever with a huge fanbase. Black Peter Parker cannot.
Why would it be arbitrary to tell a story about a Black Superman or more a Black Kal El? You may not like it, or think it's right, but that doesn't mean this film will be arbitrary.
You're also assuming you know the motivations behind the creator of the project and assuming it's for the "sake of inclusion" when it could be that whoever came up with the story had a great pitch for a film about either an original Black character who becomes Superman, the 2 other black Superman characters, or a great story examinging if Kal was Black.
As much as you can point to War Machine Riri Williams, I can point to Nick Fury, Ned Leeds, Iris West, and several other characters who are played by POC. Creating new Black characters doesn't preclude Both versions of the Flash from casting Black actresses to play Iris, Sam Jackson to play Ned, Mechad Brooks to play Jimmy, and so on and so forth.
As far as changing identity and background Tony Stark or Peter Parker would go ,by casting an actor of another race ,assumes a heck of alot. It assumes that they're aren't shared experiences across different races ,and it also assumes that people who make up a single race all have the same experiences, and the same vantage points.
There are Black nerds and teens who feel alienated , and struggle with day to day life just like Peter Parker does. It happens to Black teen males everyday , and you wouldn't lose that by casting a Black actor instead of a White actor.
A Black Peter who loses his Uncle to violence, which also happens to Black Youth's as well, is not out of the realm of possibility.
There are also lots of Black Kids, like myself who had two parents in the home, and lots of White Kids who only have one . Miles's home life is not exclusive to being Black.
At the same time, you can have a Brilliant, cocky, Black scientist who's rich, who creates a suit of Armor. Neither of these things are impossible.
The qualities you've mention about Peter , Miles, and Tony aren't exclusive to any one ethnic group.
Assuming a Black Peter couldn't have a fanbase also assumes alot since we haven't had one.
I don't doubt there would be fans who wouldn't like the idea of a Black actor playing Peter, but their preference for a White actor doesn't mean their belief would be shared by the majority of people who'd watch it.
But even your examples of Tony and Peter don't really hold up in this case ,since this new film is specifically an
elseworlds story about a Black Superman experiences . It's not part of the DCEU, and it does what you argue should be done with Black original characters: deals with their experiences specific to him . It's its own story.
Which is why , again, it isn't an either or proposition.