My two cents.
Concise version: canon ending holds that Shepard fights off Indoctrination (as seen during the current ending with Destroy option), wakes up in the rubble. Fights Harbinger with allies and war assets, goes up to Citadel (with love interest if there there is one). There, he kills Illusive Man, discovers that Catalyst is means of ordering Keepers to finish (building/programming) Crucible. Crucible's primary function is to destroy all advanced civilization in galaxy, destroying all Reapers and sacrificing all developed races but leaving undeveloped ones untouched, which will evolve in coming centuries. Shepard becomes both destroyer and savior of galaxy.
Long description: The Crucible is something that has been in the works for many cycles. It makes sense to me, then, that everyone who worked on it had to think about what it was meant to do - not simply saving themselves, or their planet, or their people, or even the current iteration of the cycle: it should mean saving the galaxy from the Reapers, and by extension, from the terrible cycle of Reaping. Everyone is fighting against the Reapers knowing that they may have to give up their lives; for many of them, that's the greatest sacrifice they may be called on to make. But my Shepard isn't like them; he got where he was by looking at abstract values, by focusing on what's important beyond the here and now. He's no longer just a commander of the human Alliance now, he's essentially the commander of the entire galaxy. He has to be willing to make the hard choices, like he told Vega and Garrus, by sacrificing those fighting with him. The ultimate cost, then, is that all advanced civilization in the galaxy must be destroyed (as collateral damage caused by the Crucible in wiping out the the Reapers, while leaving untouched any infant alien races that haven't evolved), in order to give future civilizations a life without fear of being Reaped.
If Bioware never releases another ME3 DLC, my own imagined "canon" ending might go something like this:(1) Shepard fights off Indoctrination by choosing the Destroy option (as played through my current ending) and awakens in the rubble of London.
(2) Joker, Cortez, surviving associates and other war assets (e.g. the Rachni Queen, who I'd been expecting to make a combat appearance) come in to distract or fight off Harbinger, who is still there defending the Beam. People will die, and Shepard has some choice in deciding who takes the brunt of Harbinger's fire. This gives Shepard the chance to make it to the portal.
(3) With Harbinger temporarily disabled/crippled, Shepard ascends to the Citadel, possibly with allies and/or Anderson (and if the Normandy makes a [crash] landing, you can choose your teammates from the survivors). If there is one and (s)he is alive, Shepard's love interest should briefly request to accompany him, though you can deny her this.
(4) Shepard finds the Illusive Man (who is already there, as stated by the Prothean VI, despite the arguments that his being on the station is illogical). The Illusive Man begins to make the same arguments he put forth during the hallucination ending, but Shepard cuts him off, having already fought off Indoctrination in his mind and now being resistant to it.
(5) The Illusive Man then reveals that has become integrated with Reaper technology, and gives up all pretense of retaining free will. With help from the Keepers, he traps Shepard in a labyrinth-like area of the Citadel that has never before been seen (which seems possible to me, since nobody has ever discovered where the Keepers come from). As the Keepers rapidly construct and deconstruct obstacles around him, Shepard and company must defend themselves from attacks from husks (the Beam had been teleporting bodies into the Citadel, after all) while staying on the move to prevent from being killed by environmental hazards continually being put in his way by the Illusive Man.
(6) Shepard finally makes it to a command center of sorts, where the Illusive Man is at the controls. If there is to be one, a 'final boss fight' could occur against the ally you left to die on Virmire, who is now, like Saren was, just a Reaper creature. (In this case, I'd assume that Saren recovered the body after he left Shepard, but before the the bomb detonated and he fled Virmire. Sadly, this plot device would make much more sense if it were hinted at earlier). We know that the Reapers use this method as a means of psychological warfare (see Javik's story), and Saren could have ordered the Geth to pick up the body back then; furthermore, it was never proven that (s)he was killed outright in the gunfire. Such a battle could also include other sacrificed allies whom the Reapers could plausibly have recovered, as well as anyone who was on the Citadel; in my case, an Indoctrinated Aralakh Company could show up, along with those who aren't influenced by your choices (e.g. Commander Bailey). On a personal note, I don't feel that there necessarily needs to be a boss fight at all, but I guess a lot of people were expecting a showdown of some sorts (with Harbinger, mostly).
(7) Shepard kills Husk-Kaiden/Ashley and any other enemies. The Illusive Man is then killed, and he utters the same words and dies in the same fashion as he does in the hallucination ending.
(8) Shepard goes to the console, and realizes that the Catalyst is a machine (or VI, or AI?) that can command the Keepers, who are the only things who can put the finishing touches on the Crucible, which is why they needed the Citadel in the first place. Shepard is now given a choice as to what he can command the Keepers to do to the Crucible:
(9a) Shepard can cause the Crucible to destroy all advanced civilization in the galaxy. This will disable, but not destroy, the Mass Relays, by using dark energy to overload all existing technology and advancement, and killing anything alive or active relatively near by. The Reaper threat will be permanently eliminated as a result, but the only species that will survive are those that are still in the infancy of evolution. Thus, Shepard will sacrifice everything in the current cycle for the sake of all others who will exist in the future, to give them a future free of the Reapers forever. This is the original intended purpose of the Crucible. In this scenario, Shepard shares a moment with his love interest if she's with him, as they hold each other to the end.
(9b) Shepard can modify the Crucible to explode, thereby killing himself, all the people stranded in the system (Earth being the first to go), and the majority of the Reapers, which had come to defend the Citadel and assault Earth (as the Prothean VI put it, the Reapers have 'consolidated' their forces there). If he chooses this option, Shepard first gives Hackett the command to retreat, telling all friendly forces to get as far away from the Sol System as possible. In this way, Shepard tilts the war in their favor by essentially turning the Citadel/Crucible into a dark energy bomb deployed in the center of the Reaper fleet. There should be an explanation (beyond simply genetic diversity, or at least elaborating on that point) as to why the Reapers valued Earth enough to focus their attention here. In this scenario, if Shepard's love interest is still alive, he contacts Joker or one of his surviving associates (Miranda or Jacob could be candidates) and asks them to make an emergency pickup at the Citadel. Before they finish discussing this, his love interest will beg him to take the shuttle instead of her so that he can escape while leaving her to finish the job. Shepard can use a renegade interrupt to force her onto the shuttle, or simply tell her to live for him. He may also choose to grant her request to stay with him, and they share a moment together before the end. On the other hand, if Anderson is still alive, he may be the one to stay behind, and he tells Shepard to lead humanity and ensure that the Reaper War does finally come to an end.
Just some brainstorms that I'll probably want to edit later, hope they add something of value to this discussion. Thanks again to Bioware for a great ride, and thanks to the community for making this sort of post-game movement a thought-provoking one.
Modifié par Scathelock, 21 mars 2012 - 09:38 .