Undead paladins would be the only option to me but they’re not touching races this season. I want to see it as a hero class like the original idea from vanilla development. Get to lvl 40, do a questline, let’s say you get tricked by a lich, arthas kills you, raises you as a death knight and you manage to escape back to try to rejoin your faction, have a small death knight hub outside of cities to train spells. Make it much more barebones than wrath version, as if they created it for vanilla. Runes belong to the runemaster class, they just merged it into DK. Add more hero class ascendancy
Blood elves are really dependent on TBC lore. Undead high elf still fits in classic lore, just look at Sylvanas. I hope if they ever do anything big that it’s a different timeline so they have more creative freedom.