With a picture like that im surprised you not saying Make 343 great again. 
Imagine your a lone odst whoβs pod landed in the snowy mountains of zeta Halo. You have to find safety avoiding the banished patrols and well the environment.
I would like to see Halo 5 again. Make a spon off game based on the HCS settings
An insurrection focused game could be interesting if done well or even a more story focused game in the same vein as the Kilo-Five trilogy could be great.
A game focused on the Rebels fighting against the UNSC.
Each individual boss can be a Spartan 2 hunting you down. The boss fights would vary by each Spartan having a different piece of equipment or armor ability from one another.
Halo: ELITE
Codename: Arbiter
Follow along a story of betrayal and vengeance, when Arbiter looses everything he makes a choice. What the effect of this decision has on the covenant journey. Noone knows, but itβs up to you to find out.
As you play this elite on a stealth mission to kill everything and anything standing in his way remember your actions have consequences and/or rewards in this never before seen halo, where your decisions decide your ending. And impact your legend.
/\ the idea I got reading this comment