I'll be simple and blunt: I wasn't happy with how Halo 5 played out. The story felt poorly-written, the game lacked the charm of the older Halo titles. The graphics were good, the scenes and sets were amazing, but it just didn't feel like a Halo story in the slightest.
So... I got to thinking. You guys (343 Industries.) can't be Bungie. Or, rather, you shouldn't -try- to be Bungie. You need to make your own, unique mark on the game series. Unfortunately, so far, it's not been spectacular. Halo 4 was acceptible because it was your first true steps with the Halo series, but Halo 5 somehow feels -less- than Halo 4 was.
So... Why not take the game in a different direction? Knowing that I just said you shouldn't try to be Bungie, what about making a game with an open concept like Halo: ODST was? To everyone else, hear me out.
Halo 3: ODST was unique in the fact that it wasn't like any other Halo game at the time. You played not a Spartan, but an ODST. The campaign was semi-Open World. Your character, while silent, had plenty of direct interaction with other characters otuside of 'Give me a weapon' and 'I'm gonna shoot that'. It had humorous story, but with a serious tone. Your squad was lost in the city, and it was up to -you- to find them.
What I'm suggesting is similar in many ways. Take the open-world concept, and apply it to the earlier days of the Covenant-Human war. Take a step back, show us, the fans, more of the Halo universe. Let's say there's this planet, before the fall of Reach, that used to be an Insurrectionist stronghold in the Innie wars. It holds strategic value to the UNSC, just like it did to the Rebels back then, and now the covenant are invading.
You play a Spartan II, and your squad is assigned with holding the capitol city along with a contingent of Marines and ODST. This provides several oppertunities for story-telling: Allowing us to see the interaction of the early Spartan-II units when mixed amidst the Marines and ODST, while giving us a narrative of the 'heroic saviors' here to push the Covenant back.
The game world would be semi-open, much like ODST, where several segments of the city are open to exploration at any one time. You would be stationed at a 'base camp' in one portion of the map where you can re-supply ammunition for basic weapons after missions, requisition heavy weapons with tokens of some form found in the campaign (X tokens found unlocks Y weapon for use.), and otherwise provide ambiance. Conversations between Marines and ODST about the Spartans, the conditions they're in, so on and so forth. Missions would be positioned at various points in the open-world, and initiated by simply traveling to them and activating some sort of trigger. This lets the player decide what missions to do in what order.
After a certain number of missions, you advance in the story by taking part in an assault on a Covenant stronghold within the city. After this operation, there's a small portion of time skipped, and you're given a new section of the city to fight in and conquer.
However, your squad of Spartan-II's was also stationed on this planet during the Insurrectionist war. After certain missions, optional objectives would take the form of flash-backs, in which your Spartans would fight their way back through the location they just fought in. This time, however, it's a glimpse of what combat and missions were like in the Innie days of the city.
The final (And perhaps most important detail.) of the game idea is that each 'chapter' is told from a standpoint of your Spartan talking with medical officers about the event, which would offer us a look into Spartan-II psyche. To put it into better words, the entire game's campaign is a recollection, a debriefing to the medical officers to ensure the Spartans are still fit for combat.
A big note here is that the idea of the game is to give you a personal take on the Halo universe. Rather than having a corridor shooter, give us something that lets us take control and actually be behind the wheel for portions of the game. Let us make our own decisions about where to go and when to do missions. Give us a look at the horrors that Spartans had to commit during the rebellion, and the effect it had on them in conjunction with their training.
There are other, smaller details that I would like to see included in a game like this. The ability to have your Spartan's gender have an effect on the gameplay (Fully voiced Spartan lines, male or female.), letting your personal armor for multi-player be used in the campaign for -all- the coop participants. Small things, like that. Best of all, this fits into your new squad-based combat that you've introduced in Halo 5: Guardians.
To end a rant, I just want a fresh take on the Halo universe from a company that has it in them to do so much better. Don't feel forced to follow in Bungie's footsteps, step out and make the series your -own- thing. Show us what -you- can do, don't force yourselves to use the same characters. As much as I love the Master Cheif, it's time to let him lay down and rest. His fight is over, done. Give us a new champion, give us a new story. Show us what the Halo universe can truly be in all of it's glory. Don't limit us, and yourselves, to one small -sliver- of the full picture. Even if this concept is laughed at, even if makes no sense, even if it seems utterly ridiculous, you have the ability to make a game like this and to do it -amazingly- well. Please don't waste that potential.