Having only played up to Halo 4, been trying to think of what I would've done to follow up the Bungie games if I was left to follow up Halo 3.
Story wise, I think it was ABSOLUTELY the correct decision to follow up the wider narrative about Humanity struggling against impossible odds and escaping the religious indoctrination of the Covenant by the Elites with a smaller, more personal narrative about Chief and Cortana's relationship, though I'd have probably made that narrative cover the entire second trilogy of games ending with Cortana's death and sacrifice at the end of 4 in 5 or Infinite (or 6 since this is a different timeline). I think the whole trilogy would have Cortana just beginning to show signs of rampancy in 4, ending with her separating from Chief at the end and beginning to go fully mad, leading into 5 where she's both an ally and the antagonist of that game as she struggles to help you from afar like in Halo 3 against her worst, most authoritarian impulses, ending with Infinite where Chief is assigned her replacement, "the weapon" (haven't played Infinite, but I know a little about her) or whatever it'd wind up being, and she's confronted with her worst fears expressed in Halo 4 becoming real eventually realizing what she's done and solemnly, symbolically handing over the torch to her replacement, saying goodbye to Chief and signalling her approval of the next Cortana, assuaging her fears and insecurities about living up to her predecessor.
Basically NONE of the Forerunner stuff happens at all. Specifically the reveal of them being a different species than humanity. I'm not as hung up on this bit as a lot of Halo fans, and I actually do like a lot of the lore surrounding them in and of itself for what it is, but c'mon. The Bungie games said what they said, Guilty Spark said what he said, even if we ignore that as direct confirmation that ancient humanity WERE the Forerunners, they're a lot cooler a presence in Halo if that is left to implication rather than exploring it in such exhaustive detail. Mystery, like with horror, is what makes ancient majesty so powerful a feeling.
In terms of gameplay, and story to some extent, I don't mind the Prometheans (in principle). I mean, there's nothing about them that CAN'T work with the Bungie Halo story, setting, and sandbox quality, they're just executed poorly.
They're variants on the Sentinel faction, they're robots built to counter the flood. Weapons and tactics to counter the different flood forms. There's be a lot less annoying bullshit. Knights would still teleport, but the animation would be telegraphed earlier to give players a chance to kill them first, and they'd have a longer cooldown between jumps. Watchers would still catch grenades, but sticky grenades would kill them. Crawlers would remain untouched, they're the sentinel equivalent to Flood infection forms, you want that sort of swarming one shot kill enemy in the sandbox for automatic and precision weapons. Like popping bubble wrap.
The weapon sandbox, specifically the Forerunner additions, would be a lot more diverse in their roles. There wouldn't just be 3 roughly similar sandbox variants because why the FUCK would the ancient alien god people have any version of a pistol? Humans and Covenant have those roles covered squarely. No, with the lore in mind, the creators of the Halo rings would have a lot of crowd control weapons specializing in dealing with the Flood. More powerful versions of Sentinel beams, flamethrower like area denial weapons. Maybe a gun that shoots big energy blades for cutting through Flood hordes? If they HAD a shotgun equivalent, I'd imagine something more akin to the Gravity Hammer, for pushing back large groups clustered together instead of a concentrated blast for dealing with single enemies. There'd be a lot less precision weapons, which you'd get from the humans and Covenant anyway.
ALSO Forerunner vehicles. Crazy how we never get to see any. I know they can teleport, but they'd also have reasons to want to move quickly WHILE attacking. Antigravity stuff, maybe more flying vehicles than the other factions? Vehicles with shields for ramming crowds? I dunno, missed opportunity.
For the level design, there'd be a lot less "press the 3 buttons to progress" type stuff. Missions would be more organic "meet up with this group to relay information" "Kill this high priority target", "Defend this territory until support arrives", stuff like that. I'd also open up the levels more for exploration, fewer hallways, more big open spaces. Maybe not CE level big, but c'mon this is the first time we've been on Forerunner architecture that wasn't directly connected to a Halo array, let me look around more. Not open world till 6/Infinite, and I've outlined how I'd do that before; fully explorable Halo ring, Dynasty Warrior style factioned area capture mechanics, seamless transitions between areas accessed on all terrain including air, sea, and space, but not amusement park guided experience either. We're telling a more personal story with more personal emotional stakes, the world should be somewhat more intimate to reflect that. No Ubisoft style open world either, no warp towers, waypoints, meaningless busywork, entire gameplay loop and world design should exist to enhance the INTRINSIC qualities of Halo's core sandbox shooter mechanics, not add a pointless checklist disconnected from them.
Going back to story, I do think Halo 5 should still have the Spartan IV's chasing a rogue Chief as its narrative. Because that's sick as a fuck, and gives an opportunity to get out of his head and look at his relationship to Cortana as well as humanize him more as a character separate from the Player's control. I've heard Halo 5 butchered the idea sold in its marketing of that, but my GOD that would've been so cool. Make Chief an antagonistic force you have to contend with as a UNSC soldier, show us the lengths he'll go to protect Cortana. Not a VILLAIN, his highest priority is still protecting humanity, but outside of that show who he is when he's not at the UNSC's beck and call. Swap perspectives with him and Locke, where some missions are him alone, and some he's allied with Elites against Spartans, and then have you play as those Spartans in those conflicts. Make him the single most difficult, capable enemy NPC the series has ever seen, show what a force to be reckoned with he is from the other perspective.
Make Johnson's plea, his COMMAND to not EVER let Cortana go mean something. Let it be the heart of the whole narrative, of this child soldier finding his place in the universe as a human being, not at the beck and call of his handlers. Let the story show that he is a hero not by necessity, but by choice, that even without orders, he would have still fought through the threats of the Human Covenant war all the same.











