Have they not considered anything like this? Instead of the grimoire system from D1, why not have a “Loremaster” or Librarian at the tower in which you can unlock and view events? A timeline. Some would be simply for completing things and would unlock all associated lore, others could be secrets discovered from scanning things in the environment.
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Getting lore pieces, scannables, enough activities conpleted, killing certain types of enemies x amount, completing armor sets/weapon collections/exotics would unlock lore related cinematics. I would pay for this.