Wasteland: A desert forge world. Contains forerunner ruins. Players have the option to use an effect called "dust storm" of varying magnitudes, making it very dusty and drastically reducing visibility. On one side is a series of crashed UNSC ships, on the other is a small Covenant ship, and smack-dab in the middle of the map is the one, the only, Pillar of Autumn, crashed, of course. The only problem would be the huge cliff it's hanging off of. In CE that thing had to go a mile down, at least. Easily the largest of the Forge Worlds, provided it gets made, which it probably won't.
Eternal: A space themed forge world. Takes place on the surface of Earth's moon. Two cruisers, a UNSC and a Covenant, orbit overhead. Both are enterable, and can be forged inside of.
Apocalyptic: A post apocalypse themed forge world. Think Fallout but without all the 50's. Takes place in a rural wasteland. A few small buildings and shacks dot the world. Contains a burnt out forest. Is mostly flat, but has large hills and plateaus in certain places. Has a small town near the center. Entire buildings, such as the aforementioned shacks, are forgable. Contains similar effects to the aforementioned dust storm
Utopia: City themed forge world. Contains, obviously, a city, which itself contains a small plaza, a large construction zone for building, and a huge industrial park. Like New Mombasa, has an underground. Also has a sewer system. Outside the city would be grassland on one side, with an ocean on the other. All buildings are enterable, and contain multiple floors. Contains trains/monorails/subways, and while they can't be directly controlled, you can enter them and tell them to go forward for quick transport. They need a minute to recharge after circling the map once to prevent spam.
Machinarium: Forge World on a Covenant factory planet. Mostly a mountainous wasteland, but in the center is a huge factory. Go below the factory and there would be the map Assembly, except now it's XBOX HUEG, (As in you can go beyond the little platform you were confined to in Halo 3) allowing you to leave the standard area of play and go out to other parts of the factory. Guns and vehicles are being manufactured in machines as gameplay progresses, so there is never a shortage of ammo. Machines can be told to manufacture different weapons or vehicles in forge mode, but can only be set to make Covenant weapons and vehicles.
Megastructure: Forge world inside of a megastructure, aka big-ass building. Has multiple floors, each roughly a square kilometer. Floors are connected by a series of elevators, or if there are falcons or other flying vehicles, you can ride out the windows and up or down to the next floor. Elevators can be disabled if a small map is desired.
Tundra: Arctic forge world. Speaks for itself. Contains Avalanche as one part, Lockout, and every other snowy Halo map that I don't care enough about to remember. Snow and blizzard effects available.
Infinity: Forge world inside of slipspace. Terrain includes lost cruisers, asteroids that somehow managed to enter slipspace, and small forerunner constructs.
Archipelago: An ocean themed Forge World. Contains many smallish islands, while in the center is a huge island, which resembles Death Island from the PC version of CE. Contains unique water vehicles not found anywhere else.
Construct: Forge World in a human factory complex. Contains many buildings, but also has small outside areas. Guns and vehicles are being manufactured in machines as gameplay progresses, so there is never a shortage of ammo. Machines can be told to manufacture different weapons or vehicles in forge mode, but can only be set to make human weapons and vehicles.
Divine: Forge World inside of High Charity. Contains the main city, the entirety of the High Charity campaign in H2, the hanging Gardens, the Valley of Tears, the Council Chamber, the map Gemini, the Maloseum of the Arbiter, and the Sanctum of the Hierarchs. The map would be massive, perhaps even larger than Wasteland.
Gardens: A large, aerial forge map in a swampy area. Imagine Guardian, but split up into many different parts with many platforms.
Aether: A levitating map. Contains the facility that served the Heretics as a base in Halo 2, in addition to many other facilities. Has additional flying vehicles, such as pelicans, phantoms or transport falcons. The skybox isn't brownish-red like in Halo 2, but rather a clear sky, though the effects you can add change that.
Tainted: A flood-themed forge world. Contains Backwash, Containment, and every other flood-themed map in Halo. Can be set so that Flood will spawn, adding an additional challenge to multiplayer matches. Effects such as fog or spores can be set.
Underworld: A cave-themed forge world. Tight quarters in small caves with giant chambers dotting the map, including whatever the hell that one was from Halo 2. You know the one. Is very dark, and floodlights are placeable to increase visibility if desired.
Cinder: A forge world taking place on a glassed world. Water is replaced by acidic pools. The closest things to buildings that exist are destroyed remains. Contains an underground base that managed to escape damage. In forge there is a toggleable glassing beam that will occasionally rake the spot of your choosing. Anyone caught nearby will be vaporized, and even those across the map will loose shielding. The only way to avoid harm is to hide behind hills or in the underground base. Glassed areas become volatile for a minute or so after their glassing, and anyone who comes near will take damage.
Shroud: A forge-world taking place an abandoned shipyard in Reach orbit. Two sections, low gravity and normal gravity play areas. Has an exclusive Sabre spawn option for space combat. Sections of the station can individually have their gravity turned to low, or even disconnected from the main station. Majority of map is small hallways with large ship-building and docking areas.
Those are good ideas, but would take alot of space
but if possible and eliminate others,
the huge map with crashed ships,the glassed planet, the flood area, the space map, the icy planet,and the heretic level should stay.
all of this was stated by a guy on bunjie, i stated the ones i want most in the sentence above from priorty to me to least.
the others should be able to fit somewhere on these maps in my opinon