I had a dream, a dream unlike any before,
I am not a dreamer, never once about Halo 4 I’ve longed for.
At witching hour, I dreamt of a city deprived of it’s control,
A city with a map, among which aghast shapes patrol.
Killing these apparitions would unlock new realms and brawls,
Unlocking them all would unleash that which crawls.
I think I’ve just had a premonition of ODST 2 and there may be an easter egg involving many Crawlers! Quite odd, I haven’t had a Halo-related dream in years!
Dreams (mostly normal dreams in the night of course) are like something like thinking without borders of the annoying room, time or logic. If you wake up this things will be “added” to make the dream “thinkable” here.
I think that’s why they are so useful … I mean the stuff will be added with feelings, too. And we “only” have to add stuff around them in the real world that would fit good to them and we have an unique feeling for something. 
(And I don’t mean everyone will have the same feeling btw … that makes things a bit more difficult …)
With art it seems “easy” … and Halo is some kind of art.
The other ideas might fit into the game aswell.
And I think … for an ODST-2 game. We sure need an open map. Well … it might work like: one mission to the next mission, too.
But: I hope more for an ODST-2 with a more open space. Maybe even a little bit RPG-like.
You can get a vehicle and carry weapons with it if your ammo runs out (or something like that). A bit like the Gunship Pelican in H4 just with using it for a longer time - and maybe change weapons.
… so the unlock stuff might work - especially if the campaign would be longer.
[EDIT: would also good for local coop- imo]
And the thing with: deprived of it’s control:
sounds like a plausible general idea for a storyline.
Maybe the Didact (or someone else) want something of the city (artifac, or something more software like?) … and he needs to seek it.
Maybe it is some kind of key for an installation that could cause a lot of problems: maybe the installation of “Solace”, or a weapon-installation or … this could be anything
That would explain good why the city gets attacked and lost of its control.
… I also hope that the city won’t be as damaged as in ODST-1. We had that already. Maybe a more bright place with weather - don’t need to be on earth I guess.
What you (Saint) referred to with an artifact in the city: A Composer, perhaps?
The Didact likely isn’t done with trying to harness Humanity.
> What you (Saint) referred to with an artifact in the city: A Composer, perhaps?
>
> The Didact likely isn’t done with trying to harness Humanity.
Well … I dunno. I think I let it open.
It could be everything that could be used against humans. From a composer, over other weapons to other (new) things that can “cause problems”.
In the topic ‘storylines’ I put my trust in others … I dunno to much about the Halo lore or similar things. I just try to show possible ways up that can be used good