The classic Western is a racial mythology. Integration finished the classic Western, though it took television, a very reactionary medium, some years to notice. No modern Western can get away with reducing the native Americans to savages joyfully slaughtered, or even vanishing noble savages sensitively mourned, the occasional enlightened variant. Putting the African Americans and Chinese back into the landscape paints the American Eden in different colors.
None of your objections are relevant. A perfectly good Western could be made from the perspective of a black character. It's probably already been done, in fact, I just haven't heard about it.