Oh, that is such a bad idea from a game design standpoint. You want to have a completed forge base map first, then build custom maps on it. No offense to 343i, but Halo 5's forge maps looked hideous from anywhere outside the play space. This is because they made very limited use of the existing map, and thus the base map and the custom map weren't blended together. By comparison, Reach's custom maps looked great, both inside and outside the play space, because Bungie created the base map first, and then built the custom maps around it.