Now that i have all of your attention.
If you hold down the melee/assassination button an extra bit longer, it should lengthen out the assassination. This makes it so much more humiliating, however as you're being cocky, it still lengthens the time you can be stopped. The extra half second whilst you pause before the kill will feel incredibly satisfying.
(This is do-able for the next update we need to get 343 to see this and implement it in now!)
The energy sword should be in the armour abilities section, along with the rest such as hardlight-shield. So activating it would pull out your own personalised energy sword. "intended to express its owners personal skill, clerical honour and combat viability." Bungie's words not mine. Naturally it would have to charge just like the rest of the abilities. Yet it should be only unlocked at a higher level and once unlocked you would then play for customisation. It would work well in a stance and new assassinations would look sick with it, especially if combined with what i mentioned above.
(Halo 5?)
Explosive game-play mechanics where you can be knocked over and stunned by explosions, yet not killed. Explosions would be bigger, yet the weapons and grenades harder to use skilfully and harder to acquire.
*cough cough* realistic *cough* real combat.
Thoughts? Feedback? I want 343 industries to see this!
