Conductor Min-Gi AU is interesting because he would have obvious parallels with Amelia, but he’d also be coming from a really different perspective.
For one thing, Amelia’s attempts weren’t just about her love for Alrick - it was about her desire to go back to the life she originally had. There’s heavy overlap between “I want Alrick to be alive again” and “I want to be happy the way I was when I was with Alrick”, and Amelia was definitely feeling both, but imo Amelia’s motives (especially as time went on and she got further from that period of her life) leaned more towards the latter. Ryan’s role in Min-Gi’s life would be more complicated… Ryan and Min have a past together (almost their whole lives!) but what Min-Gi would really be mourning would be the future they dreamed of but never reached. Which would be so weird and complicated for Min. Plus, the show is ultimately ambiguous about the full nature of his relationship with his parents, but it’s clear he loves them and misses them when he’s on the train. So unlike Amelia, he wouldn’t feel there was nothing for him off of the train. The nature of the life conductor Min-Gi would be trying to create/recreate in a car, and how he felt about his mission, would be very different and more complicated than Amelia’s feelings (at least as they have been portrayed so far).
Also, I don’t think Min-Gi understands Ryan the way Amelia understands Alrick. Amelia and Alrick were totally on the same page when he died, as far as the audience can tell. They spent most of their time together, they had built a life together they were both happy with, they understood each other completely. Ryan and Min-Gi are in a transitional phase of their relationship and have fallen out of touch when we meet them. They need time to get to know each other and how they’ve changed. They have a powerful and deep bond, but they’re still working on building the kind of life partnership that Amelia had with Alrick. And honestly - they’re so young. They still have so much to learn about themselves, much less each other. Amelia didn’t know everything about Alrick, because they’re two separate people, but Min understands even less about Ryan, even at the end of Book Four. So Min-Gi trying to figure out a car that has Ryan in it would be wrestling with his own understanding of Ryan and what he thinks and feels about Ryan, and maybe even trying to make the “real” Ryan and not the Ryan he wants or misunderstood Ryan to be.
I also think there might be something interesting to Min-Gi as an artist working with cars, as opposed to Amelia the engineer. I’m sure Amelia’s skillset and background knowledge give her a leg up on him, but I think a writer could flesh out the car-building process in a way that could interestingly give Min some advantages too. And One-One seems to really like music… that might not have any deeper connection to train mechanics than simply what we’ve already seen (ie he controls the stewards + porters with a little jingle and there’s lots of cars with music themes or music challenges), but there could be something there to explore with a musician false conductor.
