Althought dks creation is totally different and the process is different. I just don't like death knights on paladin-light kind of races, like lightforged still infused with light on cosmetic options but necromantic at the same time. The first death knights ever were created actually by guldan, made from the bodies of knights, and they could not contain any light holy magic whatsoever. But again, Lich king would turn them all into death knights, regardless the race and class as long as they were killed by him.
Now who is actually turning all races into death knights now exactly? Even Bolvar lost his power since the helm was broken, how will this happen exactly? That's something i didn't look into.