I am going to start off explaining myself:
I love Halo (like many others) and have had it be a part of my life growing up since Halo 1.
I want the Xbox One to do well because I belive it has innovative ideas and games that I want.
I (and I assume many others) bought an Xbox 360 almost solely for Halo 3, even after Gears of War became big. Halo 3 is ranked up with some of the most highly respected games that I consider masterpieces on their own and most of those contain a significant nostalgia factor now.
Halo 5 can be the next Halo to make people want to buy a console just to play it.
Examining the previous Halo games:
Halo was revolutionary and introduced great aspects to the industry. I won't need to say much else here, except that the maps for multiplayer were expansive, and had a certain element of awe in their design that helped to make th overall experience fun and enjoyable.
Halo 2 refined many things and introduced fun weapons and dual wielding which made firefights a little more creative in some instances. The only got some balancing issues wrong with the sword and it's infinite use and the rocket launcher in some cases.
Halo 3 was the first Halo on that gen of consoles and offered such a complete experience, it was a must have and must play. I still play it every now and then.
Halo 3: ODST introduced firefight, which had some great potential, but was still fun in it's own right. The campaign was interesting and fresh, even if it was short.
Halo Reach got some improvements right and some things lost their magic, but the Forge in this game and Forge World, when combined with custom games made some of the best elements of the franchise (and ones that were key to Halo 3's success) even better.
Halo 4. I don't have much to say here. Spartan Ops is a good idea, but the execution could have been better. Lack of features from previous games still haunts this one.
Finally, what I have to say:
Halo 5 will need to replicate the strategy that made Halo 3 into the classic it is (regardless of your opinion on it).
This means:
Forge needs to not be changed, but given the necessary resources to allow creativity Campaign needs to be hearty and satisfying Multiplayer needs to be flexible, varied, and have lasting appeal. Custom Games need to be given the love they deserve Overall package should be so complete, people need to feel like they get more than their money's worth
Case 1: Forge
Reach made the improvements that allowed so much creativity, that Halo once again found itself being surprised by the community (after the Foundry creations in Halo 3)
The only problem people had with it in Reach is that Forge World was all that was viable for their ambition and the pallet became monotonous.
Shortly after Reach came out, and people started diving into Forge World, I created a few threads about a Forge DLC that could expand upon things much like Foundry or Sandbox did as DLC for Halo 3.
A 3 Legged Goat (a prominent member of the Bungie forum community) had a thread pinned athat discussed a "Forge City" map. I had an idea to bring diversity to the environment.
Here's on of my threads: http://www.bungie.net/en-US/Forum/Post?id=2628012
The community loved ideas like those. But, Halo Reach came and went, and Halo 4 never picked up on those ideas either. Halo 4 was limited in Forging Spaces until Forge Island. That may have come a little bit too late, however.
Ever since Halo 2, custom games have been a major part of the Halo experience, and Halo 4 also lacked in that department.
Forge Solution:
Maps like Forge Halo and Forge City would be enough to satisfy most people (I assume) and another generic Forge World type map would be great as well, but not prioritized.
Case 2: Campaign
The problem with Halo Reach's campaign was the lack of memorable or amazing set pieces and encounters.
Halo 1 had mystery, and the surprise of the Flood, while 2 had some great moments, both cinematic and fun.
Halo 3 had epic enouncters and a wide variety of gameplay.
They all had a good story, but the original trilogy is what should be looked at for the overall gameplay and experience.
Another element of all Halos is the enemies. The original trilogy and ODST had a wide raneg of enemies and encounters. Halo 5 did an amazing thing with people from Retro sutios (Metroid Prime makers, that franchise considered to be Masterpieces and some of the best games ever made) to use their acclaimed ability to make fun enemies and combat mechanics to design enemies that were fun to face.
However, Halo 5 didn't have many different enemies or new things. Fighting the same 3 types of enemies for 75% of the game can be tiresome.
Bosses are another part of Halo games that are underwhelming. The final boss in Halo 4, Guilt Spark in Halo 3, and the final boss in Halo 2 were all less than stellar. No offense. I suggest taking a que from Retro studios again and look at the Metroid Prime series which has some of the mst acclaimed and well respected bosses and boss fights.
Campaign Solution:
All Halo 5 has to do, is provide sections of gameplay utilizing many different aspects of gameplay. Flying sections, driving, exploring, combat (long, short, large scale, small scale). It always helps to have diverse environments, too. The story is something that 343i is doing great with, but the campaign should be a decent length, and have a lot of replayability.
I would suggest not having the skulls unlocked from the get-go, as that was always a fun experience. The more hidden things in the campaign, the better and more replayable it will be.
Keep the enemies varied, or at least the way you fight them. Gunts can fill many rolls, from close quarters combat to sniping duels. But, the Forerunners in 5, while great to fight, became too repetitive in their use and how you fought them. Maybe a look at the Half Life series in how fights aren't all the same and never play out like other ones (due to combinations of different enemies, environments, and weapons the player has).
If there are going to be bosses, I suggest taking a look at how Metroid Prime bosses play out, or even taking a look at Shadow of the Colossus (another game heralded as a masterpiece)
Case 3: Multiplayer
Regardless of gameplay, the maps and gamemodes are their own thing. Halo always has had great modes and maps. This is not much of an issue. Is it too much to ask for Valhala and Blood Gulch in the same game? Halo 3 had plenty of great BTB maps, and Reach added great BTB forge maps into matchmaking.
I would love to see tons of great maps from Halo 1 and 2 make a return. I would also at least like seeing Sandtrap (complete with Elephants) back again. Spire was a great Reach map that would be fun to play at again.
More importantly, the weapons and vehicles are really what breathes life into multiplayer. I felt like Halo 4 was lacking in vehicular gameplay in Halo 4, partially due to map design, but also due to the over abundance of the Mechs, which are cool in their own right.
I also felt like the Forerunner weapons were too over powered, and this might not have been an issue without classes. I fell like the overall weapon pallet seemed less diverse than the other Halo games and this was made even more noticable with the focus on drops and having about half the loadout be too similar and be able to be spawned with.
I personally think Dual Wielding opened up great possibilities, developer wise. The SMG was the Dual Wield equivalent of the Assault Rifle, but singled, it was faster and better for close range, but not for long ranged. Dual Wielded, it was amazing for close range, but the recoil was so out of hand (rightfully so) that medium range was tough. This was a good balance. I also think this type of balancing could be applied to the plasma rifle and plasma repeater (or what ever gun they have like it).
I still belive the DMR, BR, AR, Covenant Carbine, and Needle Rifle can all co-exist even wihtout being weapons to spawn with (if you can't tell, I think the Halo games are more fun without custom classes)
Multiplayer Solutions:
Weapons could be more plentiful (more different weapons) as long as they are balanced.
Maps should be a main focus, I'm fine with them bringing great maps back.
Gamemodes should be varied.
Case 4: Custom Games
Here we go:
Bring back the customization options of Halo Reach, for all game modes. In the case of Infection, bring back the old options and a new one to choose whether or not to play as the new flood model from Halo 4.
Bring back VIP, alongside Race.
Don't overlook the biggest part of the community from Halo 3 and Reach that may have been lost with Halo 4.
This seems simple, but this is all that is needed. This is a very important one though.
Case 5: Overall
I'm just going to fire off how I think things should be for this game:
Firefight (with customization options from before) alongside Spartan Ops.
Spartan Ops should probably be less repetitive, and more story focused/built around unique or highly replayable encounters and objectives.
If the Flood can be in the multiplayer (Halo 4 infection) then I don't see why there can't be Flood options for Firefight. (Some waves could just be flood enemies or mixed..etc.)
Theater is great, just bring back the much appreciated and fun ability to use it for Campaign as well.
Forge in general should have a much higher budget constraint considering the new hardware's capabilities (and even use of the cloud loading features to enhance this more) and the pallet should be varied for all maps (Sandbox pallet + Forge Island pallet + Foundry pallet, with some new things...or the ability to change the look of items, at least...why not btoh actually?)
Bring back almost all weapons and vehicles, at least for Forge. I think fan favorite, the Brute Shot should return. If multiplayer is a simulation (and most likely Firefight, then.) why not have brute weaponry in the even that some like could come up in the future? (Besides, wasn't the Spiker in Halo 4?)
Co-op for the Campaign should go no where, as this is a major draw to the series.
Split Screen and Split Screen online are also as defining characteristics of the magic of Halo (and appeal for purchase) as any character in the Campaign.
Speaking of that, I'd like more traditional looking Halo armor, but that is just my view. Master Chief was almost unrecognizable in 4 most of the time, and not as cool. (IMO, obviously)
All of these things would ensure great sales numbers for Halo 5, as it is already what many were hoping for for Halo 4. It can't hurt to give your audience what they want.
Thank you for your time, please comment with any ideas/additions you have, or any criticisms. If this get's enough attention, 343i may have a look at it.
Reserved
SO, I guess you can't edit posts.
That sucks majorly, and it combined my "reserved" post with the OP.
Not very good ideas for a forum.
anyways:
TL;DR
Custom Games need their options back,
Campaign needs that epicness back,
Multiplayer needs good weapon variety and good maps,
Forge needs spaces to forge at and a wide ranging pallet,
Firefight should be back alongside Spartan Ops
If you really want to know details, read the OP.