Certain new permutations confirmed to be returning include Halo: Reach's Commando helmet, Mk V [A] shoulders, and revised FJ/PARA shin designs. The Mk V torso plating and thigh plating also seems to be making a comeback, alongside a variant-specific set of forearm plates. Also included are some permutations present in Halo: Online, such as the Breaker armour system.
It's nice to see 343i giving a nod to the old armour systems. This should present builders out there with some new and interesting opportunities for constructing sets.