I can spot influence from a few h2 and h3 maps in most scenes and we see a lot of what is clearly this games Valhalla(Blood Gultch is actually not good fyi). Don't know where you get your warehouse hyperbole.
Neither was Valhalla. There have been better large scale maps in the series, one being Containment. Similar design except one doesn't devolve into a middle of the map slopfest. Halo 3 had a lot of bad maps, like Construct and Narrows and their broken spawns/sightlines.
On the trailer, I dug it. At the same time, I can see the marketing ploy with the grapple hook. Looks cool, but it doesn't seem natural in the Halo world like it does in Battlefield. There were several issues with Halo 3's equipment implementation and I'm curious what they plan on doing these new introductions. For example, the bubble shield in Halo 3 it not only slowed down gameplay, it was used on a short respawn time. I'm not sure how these will be timed or integrated, but if they're used sporadically then it might not be as annoying or a common hindrance during gameplay.
The new weapons and vehicles look interesting enough, though we don't know too much about them. Halo Reach's Plasma Launcher was a terrific anti-vehicle design in the sandbox. Not only fitting against land and air vehicles, it wasn't an overpowered mess like the Spartan Laser turned out to be. Shame we never truly got it back.
Visually it looked much more appealing than Halo 4 or Halo 5 ever did. Spartans being shaders strikes me as a Destiny move; gonna be shitty if I can't pick my usual emblem or color choices when it's restricted behind unlocks.