I always wanted to have a time machine, that would let us take part in historic things, like the battle of Twilight gap and the loss of the moon. Maybe a raid on mercury or earth. Perhaps some huge vex/cabal war on Mars that you'd pick a side for (permanently I'd think) and that would affect loot and the state of Mars after you beat those missions. Think like the hodunk/zaford war from bl2. You end up picking one, and each side drops a specific weapon.