Many people cling to void elves as a way to finaly have high elves on the Alliance, you can't be surprised people want to play it, when we high elves have more presence then let's say gnomes. Now, I think it is way more appropriate to use Void elves as for that Reason then to request high elves themselves. That is dead end now.
We may discuss blood elves need something new or not, but there are people seriously disappointed how few new features blood elves got now, compared to other races. As for blood elves, I don't think you can make them more high elvish then they already are, so new theme comes is one solution.
As for void elves... Yes, I agree they lack on most fronts currently, so there is a lot of space for improvements. It also goes tied to their Story development, which was almost non-existent, safe for them working alongside 7th Legion during War Campaign.
As for their appearance, I agree black, white and some shades of gray are good, blonde Is not really necessary, but I guess it is likely to happen. I'd happily abandon blonde and red haircolors for good to see some cosmic colors, similar to what they voidstrider looks like. That is what could set them apart from blood elves. There are also many hairstyles blood elves already share with night elves, humans and even draenei (all of them are Alliance races, lol), so I can imagine void elves having these access to these hairstyles too, without hurting blood elves much (since that hairstyles are not unique to them anyway).