The Halo series has at least 10 years left in it's life, and I think it should go out with a bang. Here's some of my ideas:
[Campaign]
-Flashbacks from Chief's Past (It would be awesome if the game started with a flashback of John-S117 testing out the Mark V armor with Cortana.)
-Custom Campaign Loadouts (Primary, secondary, grenade, perks.)
-Quicktimes!
[Multiplayer]
-More Perks and loadout options.
-Increase the player size from 16 to say, 24.
-Covenant VS Promethean VS Human battles (8v8v8)
-The ability to take cover(Pressing a certain button would allow you to roll to a Cover Point (the Cover Point would be placeable in Forge mode.)
-Offensive and Defensive Armor Abilities (EX: Defensive= Shield boost(Overcharges shield to 1.5 times). Offensive= Overcharged motors(Speed increased by 10%).
-Prometheans and Elites as playable characters in Multiplayer.
That's all I can think of.
