I'm a little split on Forge World vs Forge Island/ other maps. On one hand I like the variety of having many cnavas's in Halo 4, and some very cool and unique stuff has been done with each. I definitely don't want to see us go back to 1 Canvas. But the current canvas's have their share of issues, such as the awkward lighting on Erosion, often overly-premade terrain (though some of this isn't a bad thing as it looks cool when worked in to a map well), and giant buildings and restrictive kill zones. Forge Island suffers from a different problem in that it is too flat. Having 1 of the islands be flat made sense but it would be nice if the other 2 were closer so you could connect them and if they had hills for different kinds of maps. Forge World didn't have many of these problems, but things did get repetitive and frame-rate could get bad more easily.
I would ask for 3 maps in the next game for forging. None of them would have structures in them unless they are part of a wall, for example one of the map boundaries being a forerunner wall made of hexagons at different heights. The spaces would each have elements of empty flatness and more interesting and varied terrain, and one map would be notably flatter than the others while one would be a bit more built up. Kill zones in forge need to be nonexistent, because we are designing the map in there, not playing it, so it makes no sense to restrict players from areas. You could have parts light up red if they are in a natural kill zone, but don't affect the monitor. Areas like the sinkhole on Erosion can just have an invisible wall to keep players in the forge space. The 3 canvas's would have different terrain and maybe a small amount of Human, Covenant, or Forerunner theme each without the entire map being these things (example: a Forerunner wall, a patch of flat UNSC style ground, a crashed Phantom.) This would give variety and would not be restrictive.