Halo 4 Forge
I have to say to definitively keep forge in with a similar style to reach, but you have to get more tools for it.
I had the idea of gravity panels, but then thought, make it so you can label it as a gravity panel so it can be practically anything you can walk on. As to say you can walk straight and then jump up n a ceiling and have it switch to your specific orientation to be on that floor but anyone else to be normal until they hit the same object.
Also you got to have panels that can move when stepped on like an elevator, treadmill, or escalator that will move to an assigned object or height.
I also think you should make weapon lockers that can be loaded with weapons instead of just being decoration. Another I could think of is Light tools, Label an object as lighted to create a lit room in a dark place so we don't have those fake looking maps that have shadows or light when they're shouldn't be.
I also got to say we need some snapping options for those forgers who can't seem to get they're seems right, need to be so you can turn snapping on and have one object snap to the edge or center of another object.
I'll post more of my ideas as I go along, but one post per subject for now