NIGHTborne. Mutated by the NIGHTwell over 10,000 years.
The original Highborne were a caste, not a race, hence used the Night Elf model, as seen in Dire Maul. And some of them rejoined the Darnassians in Cataclysm, following Archmage Mordent Evenshade as their leader.
So even as little as some extra jewelry options for the Night Elves would allow an alliance player to ‘enhance’ a NIGHT ELF Highborne (probably a mage, although it is stated in game that after rejoining some of the Shen’dralar took other trades) for RP purposes.
I doubt you could argue against jewelry, or against Evenshade being a Highborne even though he is a Night Elf? His title IS < The Highborne >.