So Here's an Idea how bout a dual release "Halo Ultimate Forge" consumers would buy disc that would enable forgers to generate the following:
1:custom landscapes (forgers pick map size and can elevate or lower landscape as well as input water, trees, cliffs)
2:building skins enabling forgers to make building look newer or worn out (Covenant, Forerunner and UNSC buildings)
3:ALL vehicles from all Halo games also include Pelican
4:A.I.'s like Civilians, ODST's, Covenant, Flood and Forerunners A.I.'s could be given radiuses that they operate in
5:Dynamic weather so gameplay doesn't get old weather on map can be rain, snow, sandstorm, blizzard, daytime, night time, dusk
6:All buiding blocks from all previus forges.
Consumers that wish to upload custom maps from hard drive to 343servers spend 5 microsoft points per map to do so as the new elements would quite a load on servers if not regulated.
As for Halo 5 premise. Halsey being held for possible war crimes flees with a group of loyal Spartans and Covenant as well as a new Cortana A.I. which houses some of the previous Cortana's memories. John heads up a squad of Spartans to bring Halsey before a tribunal and figure out the truth to his past as well as the origins f the Spartan Program. He is both helped and hindered by the new Cortana and players have t make moral choices during campaign which either turns him into a loyal UNSC soldier or if he is swayed to side with Halsey.