Things that should be destructible was destructible, not like forerunner metal. More like rocks, human buildings and weak forerunner construct.
AIs you could drop in forge world.
Head shots do much more damage, on shields too. Like in halo 3.
Smooth weapons and movements, but not so smooth like COD.
Elephants.
Bloom and a reticule that goes upwards on the weapons that shoots really long and is very powerful. Make you pace your shots at long distance, and make you aim pro in close and middle combat.
Elites playable in every playlist, make them like in reach to even it out.
Elite customization.
Make the life regenerate like in Halo 3, and make the guns actually fell like they are better than the ones we have now, like in CE.
Give us two versions of the assault rifle, one silenced with 60 rounds and a CE reticule, and one with a reticle like in reach, only smaller and with bloom and a cross in the middle(it should have 32 rounds).