There are a lot of things that I would like to see implemented in halo 5. Not necessarily all of them, as 343 can only do so much with the game. The main theme behind all these things is that I want to go back to a traditional halo game. A combination of the best of the previous games and not so much of the worst things. As bungie's second game was arguably their best I would expect something similar from 343. Halo 3 and Halo: Reach were fun for a long time. I just don't have that with halo 4. Halo 5 definitely needs some replay ability for the returning halo veterans. Halo already has a great fan base. You don't have to try to make as much money as possible. Just keep it halo and that will take care of itself.
That means competitive and social multiplayer with a skill based multiplayer (1 win = 1 exp)
No bloom
No hitscan except on the sniper weapons so people actually have to aim and lead targets
Different factions in multiplayer or at least an invasion akin game mode.
Bring back old playlists. ie. Team Doubles, Multi Team, Assault, Insane (Action Sack) game modes, VIP, firefight etc.
Reach like physics. I know that in halo 3 you could float and in halo 4 there are questionable things that happen. I think the reach physics engine was probably the best in halo. It enabled people to do so many things. The major thing I am talking about is ninjaing people. Im talking about sprinting at someone (WITHOUT SLOWING DOWN, god that is my least favorite thing about Halo 4) jumping over them and assassinating them. In reach we jumped just high enough to do that. The jump height in halo 4 is too high and you can't get close enough to people to use melee tactics.
Only 1 or 2 headshot weapons not 4. There doesn't need to be a great variety of headshot weapons just one that people like. Probably the BR with no hitscan and 4 shot kill so duels are more skill based instead of who spams and gets luckiest. Also a balanced counterpart for the enemy faction
Bring back dual-wieldable weapons. They need to be balanced with the other weapons so you don't have to have two of them to be good. Like the smg vs ar in halo 3. The smg would lose to the ar unless there were 2 smgs. They can still be weaker but not laughably so. Nothing like the halo 2 needler please.
More customizable options in forge and custom games. Like more variety of forge objects and forgeable firefight maps. Also firefight should be more team based with objectives like capturing a hill or gathering objectives around a medium sized map. Also the mode needs to be possible without infinite ammo and health, like it was in ODST. CUSTOMIZABLE INFECTION
No dynamic lighting or at least the ability to turn it off in forge mode. It is a good idea but waiting for the lighting to load when I want to test a piece of the map every 15 seconds is very annoying. Also bring back slow moving in forge like in reach. You could move slower while pressing the crouch button in editor mode.
Sprint as an armor ability again. I know spartans should be able to move but they are wearing multiple thousand pound tank armor and they can just casually sprint with it? Not very realistic. If this is the case than there need to be other comparable armor abilities. In reach if you didn't pick sprint you were at a disadvantage. Something like complete invisibility while moving with active camo, maybe a personal overshield. An armor ability that overcharges a players shields giving them 10% more shield strength and a faster recharge delay.
Tone down the power of the vehicles. The vehicles in halo are very strong. The other weapons that aren't rockets should be able to hurt them. But not like reach were a clip of a dmr was as good as a rocket launcher against most vehicles. The ghost in halo 4 is ridiculously overpowered.
If the prometheans come back they need some vehicles. Also put a human/forerunner vehicle in multiplayer. Like the Falcon or Hornet
The ordinance system in multiplayer should probably be removed. The weapon spawns on the map are key positions that shape how a map flows. It can pull fighting away from the middle of the map if the rockets spawn on the edge. Teams fight over those positions so they can control the power weapons. Personal ordinance was a good idea in theory but when one team is constantly earning power weapons one player is invincible all the time. If every couple kills they got more rocket ammo it is hard for the other team to come back.
For forge make a forge world with diverse environments. Water, desert, jungle, snow, open sky, industrial, open box, stuff like that. That way there are multiple areas. It would also have to be very large so that each area could have a medium size map in it. You could have foundry, snowbound, sandbox, abandon, complex, and adrift on the same map.
Of course new weapons. Not just weapons to fill the niches like the ar, headshot, pistol, sniper, and rocket categories. Things like the needler, railgun, sticky detonator/grenade launcher. Those kind of innovative weapons. Weapons that are just fun to use/ aesthetically amazing/ make you fell like you have god in your hand. Maybe some king of forerunner weapon that charges up and shoots a lighting bolt killing one target instantly bit only disable vehicles.
This is it for now. I may come up with some more ideas later on.