There should be no lorewise issues with merging the factions and adding a new second faction with a more flexible relation to AlliHorde for the sake of PvE story.
Honourable and peaceseeking Horde members are merging with the Alliance after the conclusion of Shadowlands. This means that all Horde races becomes Alliance members - and the Alliance now consists of all races.
“Are WoW becoming a 1 faction game now?” I hear you say. And no, it is not. A new faction is becoming a faction for warmongering edgelords and everyone who wants Garrosh Hellscream/Sylvanas/Old Gods/destruction of everything. And which faction is that? The Twilights!
The Twilight as we…