In case you don’t know, Headhunters was a top secret program: elite pairs of Spartan-IIIs sent on high risk/suicide missions during the Human/Covenant war, usually to take out high-value targets. To my knowledge, Headhunters are still active in the lore today, so this could fit with the canon-based multiplayer 343i liked to do.
Just like you saw in the video, imagine a separate mode (sort of like how Firefight was), where you can either pair up with an AI or a friend in co-op, and you both have to—stealthily—sneak into an enemy base and take out a high-value target. They can add new missions like these every week or so. The mode would automatically be set to Legendary, and your shields would be weakened, so team communication and avoidance are key.
Of course, this would obviously be added some time post-launch.
Thoughts?