I think halo should end with chief so this is my idea, This played out in my head (Not to be over-ambitious);
Cortana is panicking because she’s on the verge of death/destruction and this time it’ll be for good, so she decides that everything will go with her via use of the halo rings,
Chief calmly walks up calling to Cortana amidst her screaming and rioting and says that he’ll go with her this time as long as she does not fire the rings; He tells her that he shouldn’t have let her go alone the first time but now he’ll make it right. Cortana stops rioting and questions if he’s telling the truth which he confirms
Blue team(Cause they need more story now due to 5s lack of it) immediately begins to protest but chief tells them to “stow it”
Chief turns around takes off his helmet (camera would be at boot level to see his helmet fall to the ground next to him) camera cuts to just his eyes[which look tired and weary but ultimately at peace] as he commends blue team for being his best comrades, orders them to return to the infinity(or wherever). He then turns to start walking back to cortana who’s standing by a pillar of light (gotta figure that part out)
[At this point chiefs full body is in the Shot but you can only see he back of his head]
Kelly calls to Chief asking what he’s doing with which he replies almost calmly “Finishing the fight” [Chief enters the light with cortana on his arm]
Frederic takes a quick step towards chief but Kelly stops him with help from Linda; Frederic questions why they won’t go after chief with Kelly replying that it was something only the Master Chief could do and that he had given them a final order.
Fred walks over and picks up Chiefs helmet looking up “Its been an honor serving with you… John”
From here on to the credits its completely quiet except for the [somber] halo theme track
Blue team arrives to Lasky to report on what happened and Kelly hands Halsey the helmet in which everyone in the rooms faces are grave.
On Sanghelios, an elite runs into arbiters tent; Upon hearing the news arbiter leaves his tent and looks to the stars as he raises Prophets bane in salute.
Spartan Locke and his team along with the rest of the ship receive word over the intercom in the infinity’s ship bay; Vale, Buck, and Tanaka all look at each other in surprise and watch as Locke puts on his helmet and walks over to a window, nodding in respect
Last scene shown is Halsey in her cell, smiling sadly as she looks over Johns helmet, the camera zooms in on her face as the screen fades to black and credits roll
Legendary ending [After Credits]
Cortana and John are surrounded by nothing but light talking about the long road they had been on, How she had never guessed that their last adventure would be against once another; Cortana expresses that she had done so much wrong in the end and Chief Forgives her saying they were only human. They embrace and Cortana expresses how she had “wanted to do this for a long time” as the audio cuts completely out and the screen fades to white (and They disintegrate leaving no doubt of chiefs death).
Back on earth [or Wherever I’ve lost track of what planets are destroyed] They hold a ceremony honoring Chiefs sacrifice. the Arbiter speaks on his involvement in ending the war with the covenant. The big name characters that are still alive [Lasky, Palmer, Halsey, Blue Team, Locke and his teaming, etc) are there, a certain few give speeches but the sound slowly goes out as the camera pans upwards to a monument of Master Chief and continues to pan up until theres nothing but the stars and planets
This would be the end of halo, as the covenant has been destroyed along with the brutes from HW2, the flood had been cleansed from the system finally, the forerunner and warden had been destroyed for good as well, the halo rings were destroyed, and the rampant A.I.s had been dealt with.