"When we hit our lowest point, we are open to the greatest change"
This sounds beleivable, but like "I can't believe it's not butter" I WANT TO BELIEVE. But anyway, vehicle/weapon customization is okay if done right and doesn't drastically affect the gameplay. (e.i, just some cool detail or something)
But when it comes to armor customization...well...I like my cheif mean and green as he has always been...
I also think in terms of a gameplay feature could be like, the Dawn (frigate) cheif is in could still have some unused ODST drop pods, and the cheif could use them to access the supposed forerunner planetoid. That would be fun.
The list goes on really... I like the idea of water combat. I liked it when my spartan could take a bunch of gunfire, AND wouldn't be killed by mere water.
UNSC on the planet seems weird. especially if there fighting each other. What i think would be cool if there were "bosses" (example, Halo 2, Tartarus, Prophet of regret, etc).
Those bosses were fun and gave halo a cool different change of pace. Okay tartarus was a bit annoying but still.
And in conclusion, scarab fights, "bosses", water combat, drop pods, new weapons, new vehicles, large maps, longsword piloting, and anything else awesome that wasn't incorporated in earlier halo's. but you've also gotta have a deep storyline that goes back to the roots, and better graphics.
I'm already excited :)