Why does this matter more than the other aspects that are changed? Do you think skin colour makes people different in some deep way?
You could not have a black bond without addressing the fact that he is now black in some way.
Would it be credible to have a bond film with a black actor where absolutely no one (including bond) mentioned it?
It would therefore change a considerble part of what the bond character is
(which is a bit a throwback to days past in the UK complete with the womanising, boozing and posh old boys network that comes with it)
To just insert a black actor into this role and pretend like nothing had happened would be ridiculous.