For what it's worth, the company of actors at Shakespeare's Globe Theatre in London regularly mix and match black and white actors .. we've seen a black Duke Orsino in Twelfth Night, a black King of Navarre in Love's Labour's Lost (as well as a black female actor playing the male Moth in the same production). This is just a few memories of the productions I've seen, not the whole story by any means. It doesn't alter anything much, so I can easily envisage a black Hamlet in an otherwise all white cast.
"Whiting" up to play the queen seems to be making quite a point, though. A tad heavy-handed, as far as it appears to me on a superficial level, but I hope they have more nuanced reasons for doing this.