Nobody needs more an addition type of elves. If anything should be added to the Alliance in the form of elves, then it should be high elves the way we know them from Warcraft 2.
In addition to this, it would be a major lore setback if the high elves affiliated with the Alliance, who refused to use the fel despite their massive hunger/addiction, would now readily and with no hesitation turn to utilizing the void. Then again, I understand the difference between utilizing the void and feeding on it.
Alleria's character was unnecessarily screwed up. It would've made more sense if Vereesa went the void way.