My own list: 1: Side quests that flush out the story more. IE: - help an Exo warlock discover more about the origins of his people. - discover Human holdout settlements scattered across Earth, Venus and Mars. - An urgent mission from the Speaker to recover a half-crazed Ghost and his Guardian. 2: Make the Grimoire an in-game codex instead of the web site bs. 3: Sci-fi easter eggs: - a monolith in a Fallen excavation site on the Moon. - a Total Recall reference somewhere on Mars. - Master Chief's helmet sitting on a shelf somewhere in the Tower 4: Less trippy dialogue ("That wizard came from the moon").