The Chief retaining his "classic" look is fine. He's an established character with a visual signature that most people have a certain expectation for. While I did love the H4 and H5 design of Master Chief, reverting him back to some semblance of his original look is...charming. I do prefer the Spartan IV's retaining thier sleek, almost mass-produced aesthetic, so I think that should remain. However, 343 needs to soften the color tones, maybe wash them out abit. And use the same lighting on the character models as the level, that way the players dont stand out as bad as they did in H5.
I think that the Pelican should return to it's original form as well, it had a unique look that was reminiscent of the F117 Nighthawk, which is pretty cool. The newer ones are somewhat bulbous, and definitely have a look similar to some sikorsky vehicles.
I think Elites should have both the sleek agile look, and the bulky British look as well. Have the Arbiter return to his H2A look from the opening cinematic, but have a mix of new and old.
Most of the Covenant vehicles look better, in my opinion, with thier H5 iterations, so keeping them as they are now would be just fine with me. A return of the Plasma Rifle to the forefront of Covenant weapons would be a welcome sight, its was very unique and definitely stood out as 'alien', instead of an 'alien' approach to a human weapon.
I'd like to see the AR revert back to the MA37 look( yes, I know it's in the trailer, but it can be a place holder)it was definitely more interesting to look at, and had a great sense of militaristic feel as well. The Pistol, design-wise is fine, just needs to be more of an actual side arm, rather than a utility weapon. Lower the damage, accuracy and crank rate of fire up.
I like have both versions of the BR, so leave em in. I prefer the M20 SMG(H5 variant) and both rocket launchers- the Pilum and the Spnkr.
But for the love of god, leave the Gen 2 HUNTER armor alone, and keep it in the game for multiplayer!!!