Death knights were completely controlled by the Lich King... Felbloods willingly bathed in demon blood, and i don't think all races NEED to have equal number of sub races or even a sub race, What i'd propose is races that share a slot to the races which they are culturally closest too, but they'd also have their own class restrictions. my choices would be:
Stormwind: Humans and High Elves (same classes, BE model with blue eyes, maybe minus Warlock), Warlocks, priests and death knights could also get the Cultist type skins.
Dwarves: Bronzebeard (Paladin, Warrior, Hunter, Mage, Rogue, Priest, Monk, Death knight)
Wildhammer (Warrior, Hunter, Shaman, Rogue, Monk)
Dark Iron (Warrior, Warlock, Hunter, Rogue, Monk, Mage)
Gnomes: Uh... Gnomeregan gnomes? (Should get paladins)
Night Elf: Kaldorei Highborne (Paler skin, blue glowing eyes, can't be druids, death knights or priests)
Draenei: I don't know if they should get Broken as they require a new model, in case they should then...
Broken: (Rogues, Shaman, Warrior, Mage, Monk, Hunter)
Worgen: get gilnean humans.
Gilnean: (Druid instead of Death Knight, can't transform to Worgen. Even if Harvest Witches are tipically weaker than normal Druids, they are capable of shapeshifting, and have recently been studying with the cenarion circle.)
Mag'har (Shaman, Hunter, Warrior, Mage, Monk, Rogue)
Blackrock/Dragonmaw (Same as green orcs, they blackrocks get tattoos)
Revantusk (I don't know if they should implement bulkier trolls, but this tribe makes sense, same classes)
Tauren: Grimtotem (Rogues, Mages, Warlock, Warrior, Hunter, Facial tattoos)
Goblins: Just bilgewater.
Forsaken: Lordaeron/Gilnean (Same classes, plus paladin)
High Elven (Same classes, softer decay and upright pose, elven ears, blue eyes)
Blood Elves: They stay the same.