(Do I have it in me to attempt to recreate my first post that got eaten? Let’s see.)
Yesss, basically I think a Mad Max/Shakarian AU writes itself. Let me tell you what I would do:
First, I’d start the AU around Mindoir, only instead of Shepard escaping and being rescued, she’s taken by the batarians. See, I think it’s important that, like Furiosa, Shepard doesn’t have the authority Alliance rank or Spectre status would afford. I want a scrappy, wounded kid who is determined to survive, no matter what, who sees hell and decides to keep walking. She’s tenacious. She knows how to play the long game. Earning trust takes time and patience. Shepard’s got both. Her time will come. (I’d also like to have some backstory where she starts out a bit of a lone wolf, looking out for herself; friendship and family come later.)
Garrus, on the other hand, I’d have still in C-Sec. Only this time, when he wants to make the call to shoot down Saleon’s ship, no one countermands his order in time. So the ship goes down, with Saleon and all his hostages–and crashes right into one of the Citadel’s wards, taking out countless innocent bystanders. Garrus tells himself he made the right call, but he’s haunted by names of victims, the faces shown in endless slideshow on the newsvids. Dad or no dad, Garrus is ousted from C-Sec. He tells himself he was sick of all the hoops he had to jump through, sick of all the red tape, can do better elsewhere. But still he sees those faces when he closes his eyes. Families. Kids.