343 Industries seriously needs to take Forge to the next level. Reach was a step up, but so much more could be done.
Pelicans and Phantoms in Forge are a MUST. This has probably been the most highly requested feature since Halo 1. Guess what? It’s been nearly ELEVEN YEARS since Halo 1, technology should be able to handle pelicans. There is no way that 343 does not know that we want Pelicans. If thy want to gain the trust and love of the forging fanbase, they need to implement this.
Opening and Closing Doors: This would be a simple system. We could link buttons with doors using the same way we link teleporters. Just put a button and door on the same channel, and there we go 
Destructibility: This would be a very convenient feature. In the options for the object you select, you should be able to set any doors/walls to eother DESTRUCTIBLE or INDESTRUCTIBLE.
Weather: Whether or not we have to load a new map for different weather or it is an option in the Special FX section, we need weather and time of day settings. It pains me when I load up a map and somebody has the purple color filter on.
More Forge Worlds: In Halo 4 we need at least 3 or 4 different forge worlds, either the same size as Reach’s Forge World or larger. In fact, in order to make the wait for Halo 4 easier, why not make a DLC map pack centered around forge?