TLDR - This is not a Bloodelves change faction thread.
Ogres and High Elves. For years, we've seen these races around Azeroth with no way to play them. After the bloody coup that is the Siege of Orgrimmar, both factions will need to bolster their ranks, and reaching out to these two nearby allies will become a more tempting opportunity.
Vereesa - Her husband dead. Her adopted home now in control of the alliance once more. She's helped the Alliance in Pandaria, and she is now a more recognized character in the World of Warcraft. She would lead her people, few though they are, to a new home with the Alliance in the Eastern Kingdoms.
Rexxar - Months back, we heard that we would see Rexxar once more. Long time friend of Vol'jin, Thrall, and Chen Stormstout, now is the time for this Mok'Nathal ogre to come back and lead the ogres from Dustwallow Marsh as they join the horde, where Garrosh has made it easier to control by removing Theramor as a threat.
Their tie to each other? The return of Alleria, Verieesa's older sister from Outland, where Rexxar has been living. Something about the return of the eldest Windrunner sister has driven the ogres of the shattered Draenor to leave seeking a home with their new allies. Rexxar is angry about being uprooted when he didn't want any part of the war between the orcs and humans, but he'll do what he must to guard his people.
So, thoughts? The idea is that we're not trying to switch the factions around, nor trying to make a race neutral. It's just two more races we've already seen in WoW that are not currently playable, but can be.