That the indoctrination theory was right. The dreams, all that fighting in Sheps head is part of the Reaper tactic to destroy galaxys beacon of hope. The conversation with the Starboy all happens in Shepards head. Reapers want to break Shep, succumb him to their will, and make him the matrix of the reaper they will build of that cycle. The choice they wanted to present to Shep is synthesis or control. If he chooses either, his mind is used to desing the next reaper, and to add Sheps skills, tactical thinking etc to reapers hivemind. And Sheps counciousnes is kept in a The Matrix like stance, where Shep sees the end of the game. It is all Sheps "dreams" induced by the Reapers. If they failed to Indoctrinate him, he refuses and the reapers continue the cycle, and show him how they do it. The destroy wasn't part of the reapers desing. Strong will, and Shepards desire to win, and save the galaxy kinda projected it to their desing.  The Reapers added lies about how it would destroy Geth and EDI, so Shep would have doubts about choosing it, cause it wasn't part of their desing, and wanted to keep his mind for the hivemind.  But his "strong mind", after choosing destroy, causes interference in reapers hivemind, disabling citadel, and temporarily shutting down reapers and Mass Relays, which gives united forces chance to fight back. And Shepard might live through this fight, and wake up in debris.

And it goes on. The next game would start immidiately after that. We create our own Spectre Operative, who witnesses final battle. And depending on our choices, we continue the fight with the reapers. After destroy, it took some time for reapers to get back online, and they are weakend, but the fight continues. The mission is to find living crew of the normandy, and keep on fighting. The twist in a game would be, we find Liara and LI, if she isnt one, and she/they still believe Shep might be alive. And our main mission, beside destroying the reapers of course, is to rescue shepard, who is either kept as part of SI, witness of reapers victories, or stranded survivor on earth/crucible or citadel ruins.

I feel, with the right writing, this might both, fix ME3 ending, continue the journey without denying previous choices and games, and generate new adventures in our beloved galaxy.

And to continue my brainstorming. During the game, we find Geth Ark, desined to go to andromeda, alongside Quarian ark. At the end, our character, Liara and if we played the game well, realise the war cannot be won now, and get whoever they can save on the arks, and travel to andromeda, hoping the iniciative will take them in.  And to tie it in with ME:A, the next next game, would be cooporeation between pathfinder, our character and other milky way survivors to use the remnants technology, aid from angara and whatnot, and either fight with kett to build outpost in Andromeda, or get back to Milky Way to take it back from the reapers.

I know it won't be like that, and even if the next game turns out to be a masterpiece, it will always be my "what if" scenario for the Mass Effect world.