The only issue with the ethnicity is that four of the five are from an isolated, ethnically homogeneous population. Mat should have been less white, but in the first two seasons, he's the asshole of the group, so of course they aren't going to dare come up with a cast that lets woke critics say "Oh look, the good house nigger, the bitchy female boss who's wrong, the secret villain and the greedy asshole who almost derails everything by stealing treasure are black, while the hero gets to be white." I'll bet good money that Egwene's characterization goes right out the window, but on the other hand, it might mean they portray Nynaeve as something other than the PMSing mean teacher.