I haven’t read much about halo 4, but if it is going to have a forge, or some other map creator, then there should be an option to make objects movable. That is, they move if something pushes them. I was disappointed with Reach’s forge because it lacked this option. One of my favorite game variants from halo 3: The trash compactor, was ruined because of this. So if forge does come back, please make objects movable. The bigger the better. 
That’s all I have to say. 
you can make some movable if you set them to phased… but doesnt it not work?