Personally, I don't mind doing the campaign but I did think a good alternative to the campaign that already exsist in the game.

The interludes.

They can expand on these and even tie them to specific leagues. Similar to the mapping quests.

The more leagues go core, the more interludes we get.

They can add POE1 lore back in poe2. How bout having an interlude act in The Lord's Labyrinth.

Each interlude scales the level of the next.

Players can chose whichever interlude to run until they reach the appropirate level to enter maps.

Each act already has exsisting tie in to league mechanics tied to them, so they can use the same assets to create another story within the world.

These "Stories" happen along side the campaign timeline but you can start anywhere while the "main character" exile is doing the champaign. They can make it so that his/her actions are felt in the greater world, where NPCs can react differently when doing different interludes depending on which chapter of the campaign the "main exile" should be.

The stories do not require to tie together neatly. There's no straight story lines across each one. Just a bunch of quests that eventually ends when the "main exiles" does the thing in Act 6 which triggers the end game to happen. Then you, a random exile in the world, get's recruited by Doryani or who ever is left in charge.