I loved everything up until the ending. Please don’t waste Yrel and the Lightbound like that.
I’m all for your idea but instead Yrel and the Lightbound ally with the Arathi. You can then have Yrel with the Lightbound play a significant role in Midnight so we have a Light reprieve in a Void dominated expansion. To me, it feels fitting that if we get a revamped Quel’Thalas in Midnight, then we get a revamped Azuremyst/Bloodmyst to go alongside it. We could get throwbacks to the Shattered Sun Offensive. Patch content could be a return to the Draenei Isles with a Lightbound raid.
That said, I do also think we’re due a Northern Kalimdor expansion at some point after the World Soul Saga if we don’t immediately go to Avaloren to contest with the Arathi. So I wouldn’t be surprised to see the Draenei Isles be saved for that expansion. Northern Kalimdor could be the Lightbound Invasion expansion. But I could also see it as a return of the Legion expansion with either Sargeras playing his hand again depending on what goes down in The Last Titan or Denathrius taking over the remains of the Legion.
Either way, The War Within and/or Midnight seems a very good place to reintroduce Yrel & the Lightbound.