This has been clearly talked about in the "Forge Thread". When you read it through entirely you see it talked about in detail.
I am not trying to spam my idea, but this is my post under the pinned topic:
I would love to see improvements in forge and the incorporation of maps into the play lists. I do not want to see them become a DLC because of the obvious reasons.
One being the producer of the game will make money on a map they did not create or pay for.
Two, I feel the maps from the community should possibly have a playlist, say once a month and on a weekend, were player can go into matchmaking on them and vote on the map after a certain number of game have been played on it. Maybe it would be possible in this playlist to force single players into matchmaking there by making it easier for the system to place the players on the maps needed to vote. Once you have earned the status of voting on all maps you are released into group matchmaking status that allow groups to play together and select from a set number of maps. After it is determined by the those in charge of the game which maps are viable, voting weighing a notable part, drop them into a community forge playlist. As the votes for the maps continue by the community playing them, they could be incorporate into the regular play lists. It would help to ensure play ability of the maps and bring new maps into regular multiplay on a sustained basis.
Third, the addition of wreckage and/or "inert" ships and vehicles that would give more texture and color to an environment would be a very nice touch. It may be possible as the game is being developed certain items from the campaign or multiplayer maps could be rendered for forge while they are in creation.
Lastly, if does continue in Halo 4, it would be nice to be able to have a color pallet for the forge items, were applicable, and even the ability to make the shapes have a stone, wood, metal or natural finish. There are geometric shapes that can be added to give more range to the structure, maybe themselves having thickness and/or dimensional properties that are adjustable. The same could be applied to elements such as trees, waterfalls, and possibly a localized fog or steam. I realize that items that show movement are much trickier to implement, but who knows what is possible on a limited scale.
Not much really needs to be added to forge to improve it. Since forge has become so widely used and incorporated into the game, I would be willing to pay extra for a "Special Edition" of the game that brought us more flexibility in forge world. If there is an effort to keep forge in mind while items and pieces of the game is being created, it may be there that more can be given to our beloved forge world. Giving us more may ultimately increase the life span of Halo 4 and keep the play lists fresh with new maps, which is always a plus.
One additional thought. Possibly offer different environmental platforms such as an urban, jungle, mountainous, and areas similar to the actual campaign part of the game environment to build off of.