Something derivative of this...
Halo for me is when all players spawn with the same base traits, no changes (loadouts). All of the players have the same starting weapon. Each player has a regenerating energy shield. Each player has two weapon slots. There are set locations where set weapons appear at set intervals on the map. The player may pick up said weapons if he chooses. The whole game is built around shooting, throwing grenades, and bashing things in with the but of your gun.
That is more or less it.
Now I said derivative. Dual wielding was derivative. Equipment, poorly implemented as it was, was derivative. Even assassinations, though I do not like them, are derivative. AA's are not, the break the idea of initial equality on spawn.
If you want to make a change to Halo you should not break the base traits that define the game. Do you want a new feature for Halo 4? Add something that is derivative of the original formula. A jet pack placed on the map for people to rush to pick up would be derivative. Yes, I am not in favor of adding sprint as a base trait. That said, so long as everyone has it, then it works. The thing with Halo 4 is that not everyone is getting sprint but they are also getting the option to choose between seeing through walls or becoming invisible off the start. That breaks the rule of equality on spawn.