: Plus, if I start a new game, do I lose everything I've collected in the open
: world?

Would be nice if they allowed you to select a mission on the map and "reset" it.

Also, doing multiple playthroughs like borderlands, where the entire game resets and gets harder, but you keep all of your equipment from the previous playthrough could be neat. Though, Halo is not really loot driven, so that might not work.