They mentioned that when designing Reach they had a gamemode of something like 6v6 space battles made, but dropped it because they thought it didn't fit with the typical feel of Halo. Perhaps that was also testing for a Destiny multiplayer mode as well? In general though, I'd love to see a firefight-esque mode that's like it is in the Reach campaign of tougher and larger, more powerful enemy ships spawning in over time, and players have to work together to not die or defend and objective or something. That, as well as that I'd love to see clans get their own giant ships to store their personal ships in that can be taken into battle with other clans with the members either piloting their own ships, or controlling guns on the main clan ship, with the objective to win to destroy all enemy ships and to hit the critical points of the enemy clan ship to take it down. Preferably though this would only be for aesthetic reasons, and all the ships will still be fully functioning after the battle is over. As for simply player versus player battles in general, I'd love to see both space and planet atmosphere dogfighting, and think there should be two different versions of it: one where you get only one life and have to kill all the enemy players, and another where you get unlimited lives, but are aiming to ge the most kills like a typical deathmatch.