> 1. Theater mode for all gametypes.
That’s a must.
> 2. Invasion.
Really like the Invasion concept. Didn’t get to play much as I was late to Reach.
> 3. Larger Player count.
I don’t think that would be needed.
> 4. A more innovative forge.
Sure. I would like to see lots of improvements to the system.
> 5. Playable elites.
Sure, as long as the hitboxes are balanced with the Spartans.
> 6. Dual wielding.
I don’t think that would be needed.
> 7. Better competitive maps.
Absolutely.
> 8. More gametype options for custom games.
Absolutely.
> 9. Unlock armour through achievements.
Never liked that concept. I prefer buying it like in Reach.
> 10. 1-50 ranking system.
That is needed.
> 11. The classic halo gameplay (arena focused)
I have no problems with that as long as it is not carbon copy.
> 12. Less elements from newer fps’s like CoD
I don’t mind ideas as long as they are not rip-off. I am OK with Sprint.
> 13. Bring back old characters from the halo lore (Mendicant Bias, the Arbiter, masterchiefs old team, and maybe even Jun)
Sure!
> 14. More map remakes (more than 1 at least)
I don’t think too remakes are a good idea. People always complain about the remake “not working on this game”.
> 15. More surprises (like the drive-able pelican in halo 4)/
Sure.
> 16. No custom loadouts (except maybe being able to customize the skins of the weapon you start with. For example, if everyone starts with a battle rifle, each person will still get to pick what skin they want it to have.
Custom loadout should stay on Social playlists (BTW, those are a must too). Ranked/Competitive playlists should remain with equal starts.
> 17. Classic halo armour (like how they brought back the halo 3 scout helmet, even though I did really like the one in reach)
Well, I actually like 4’s direction better, but some armor sets are just weird/ugly/stupid.
> 18. Larger forge canvases (Make another forge world!)
Sure. Forge Island has a lot of space, but when it comes to foring on one of the islands… They are all the same except for their size and have little to no variety on the terrain.
> 19. Bring back brutes
Why not bring back all enemies and have diverse looking foes in the games? Since now all Elites/Grunts/Jackals are not meant to look all the same, I would like to see enemies/allies with different physical traits between them. Halo 3 Elite fighting Halo 4 Elite… I want to see that!
> 20. I know I might get hate for this, but… Bring back the flood!
The Flood will be back 
As for what I would like to see:
- Halo 2/3 style Hunters. Never liked Reach/4 (I mean the AI).
- Scary Flood. They are meant to be terrifying and they make me laugh.
- Black BR. Seriously.
- Some Perks are not even needed and should be a base player trait. And as I mentioned above, Ranked/Competitive playlists must not have anything related to loadouts.
- Vehciles from Halo Wars. I want to mow down anything with a Vulture.
- Longer campaign. I would like 3 paralel campaigns in fact (Chief/Arby, Crimson) But that would be too much work.
- Boss fights.
- No QTE’s. Please…
- Less spamable AAs.