Forge World? Seriously? Forge World makes my skin crawl. People say "It's so easy to build on it!" And "It's so cool!" and stuff like it. That just annoys me to no end.
Reach: Not even a world, and no flat land anywhere. So you have to make your own flat surfaces which takes a huge chunk out of your budget. The island, small and awkward. The so called "canyon", way too hilly. The Hangar and what people call "flat land" above it, too small and too awkward.
Halo 4: Finally, flat land but nothing else. So now my maps all have to be flat. Really awkward to make anything that involves natural structures because they're not there.
So if 343 actually want a Forge World, it better be big and have a mix of flat and non flat land. And none of that Covenant or Flood canvases people want, it's a terrible thing to even picture.