I just seems like petty gate keeping to me. The desire to deny others something that you yourself get to enjoy just never made sense to me. I've seen them come up with reasons such "lore" and "faction distinction" and "racial uniqueness" but it all really just boils down to "I don't want you to have anything similar to what I have" and "You shouldn't have even gotten what you got in the first place!" (referring to both the model when void elves were first added, and later the skin tones).
And the sad thing is, if blizzard does give void elves a few natural hair color options, they'll make a few snarky posts, and then move on because the subject will be closed (finally). So all this hullabaloo will have ultimately been for nothing. All they'll really have left is to use "you're not really a high elf!", "your name plate says void elf still ha!", and "you still can't be a paladin so nyah!" as taunts. I can't even imagine how apoplectic they'd get if blizzard decided to just copy and paste all the blood elf hair colors and hairstyles over to void elves (and give blood elves all the void elf hairstyles minus the tentacles thus making both races even more similar).
As far as the nightborne go, I would love for them to just get a ton more options. They certainly need it. I'd be happy even if blizz just copy and pasted most of the night elf options over to them (maybe with some minor variations).