First....a model based off a Blood Elf model is still the Blood Elf model.
Second...your retreat to biology is silly. Zandalari are trolls but they have a diffetent model. Draenor Orcs are still Orcs...Highmountain Tauren are still Tauren. Void Elfs are still Blood Elfs. KulTirans are still human.
Having identical biology does not preclude having different models.
And as I said before, the issue wouldn't be just the skeleton but the entire package. The model, the culture, the history, the look and more.
All a High Elf model need be is be recognizable as a High Elf. Nozdormu is not based upon a Blood Elf skeleton nor are the San'layn Princes. All are still recognisable as High Elfs
So...if Blizzard added High Elfs in the manner I suggested, or some other fashion which worked to create a different identity for them, would you play them?
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If Blizzard were to do anything with Dragons, I'd suggest they add Drakonids to the Alliance.
That way, I can get my Naga.