Imagine it like Skyrim or God of war or Kingdoms of Amalur where you have access to classes and you level and stuff, each dlc is another expansion from the game where main boss would be Ony, then Illidan, then Arthas, so on.
Expansions would release like how destiny brings out update/expansions.
I would SHOVEL money into this, just to play the lore again.
Obviously they’d have to scale raids into boss dungeons, take out the auction house, and make things more manageable but damn I’d play the shit outta that.
REALLY hard to say lol. There’s so much content now the game would throw you into the new expansion but for story, there’s a LOT of stuff in vanilla that I think you could skip it all and be fine.
Burning crusade was really where the narrative took focus, to fight illidan. Then same thing with Lich King Arthas, then cataclysm expansion with the dragon. Got a bit weird from there but that’s where I’d start/go if you wanted the story.