So I, too, am guessing AU Jace/Derrick Moss on the AU Marauder. Mixed feelings on that one.*
One and Corso are both dead. And the guy who could be on that ship, if we run with that, is either AU Corso or AU Moss. There is no AU One. I figure AU Corso would be too much of a "been there, done that," and don't really see an organic way to integrate him into the crew anyhow, or a good "why" for it either. They could have him reoccur as a villain, I guess, but it seems a bit pointless to me, and the seasons seem too short for that. But what might be interesting instead is if that's AU Moss. If that's the case, the dude is seriously evil enough that he was willing to nuke the miners just to get rid of AU Portia (so he's definitely not a good guy :-/), but unlike Corso, maybe he could still be "saved"? (I agree there's no saving Corso (AU or ours).) And given the Raza's crew's redemption struggle, that could prove a goal they might be interested in pursuing, and not too OOC.
AU Moss also offers a couple of benefits storywise. He can provide insights into the workings of the Corps, without being too knowledgeable (as AU), which could help with the upcoming battle, and be generally more competent than One, having not been wiped. It makes the story with the murder of Moss's wife relevant again. And it answers the question I immediately had - why would you switch universes? How would it put whomever at an advantage? But if you're AU Moss, you know you can be charged with things like bombing the miners, so no "get out of jail free card" like with One in the beginning of this season, and as with our crew last season, AU Moss probably wouldn't have the memories/contacts to survive as AU Corso or as a wanted criminal on the run, and if you thought your wife might still be alive here... Well, I find the motivation somewhat compelling, and could picture it, which helps me a lot, and the possibilities for the story intriguing, for which I am thankful.
Nevertheless, I was still a bit sorry they didn't just shoot him, whichever one he is (heh), because as a running gag, it had something. Otoh, as a meta statement, it has something, too - keep shooting him until they get it "right." Too good, too evil, just right. (Once again, fully accepting that mileage varies on what "right" may be. Also, in light of the Raza's crew's wiped status, I personally don't hold their past crimes against them, which makes a difference, but that's a seriously tricky moral issue IRL. (Think: punishment or lack thereof for mentally ill 'criminals.') But that makes any rehabilitation of AU Moss difficult for the story, because he clearly is the guy who pushed that button. )
I really hope it wasn't AU Emily on the ship, because I thought Five's/JL's performances as different characters when they were doing the flashbacks/memories in season one were some of the weakest sauce in the show, next to One's/MB's. I don't think the actress has the range for it, and I'd prefer they play to their strengths.
As the AU Android said (or more appropriately: the writers had her say), basically anyone on the AU Marauder other than AU Corso/Moss would be "redundant." I think the show runners have been kind of straight forward with their twists and hints (in part, no doubt, because the small handful of eps they have to get things done limits how much they can twist things around), so imma taking that as a pretty clear wink through the fourth wall.
(Along the lines of "lack of twists," I also took this ep as final confirmation that the "him/he" Portia and Ryo were discussing killing in that fragment from season one was in fact Jones/Varrick.)
Worst case, if the person on board is AU Moss, in this story 'rehabilitation' can always take the form of wiping him and hoping to regain One, but like I said above, I can't see the narrative advantage to that (and really hope they don't).
I'm thinking Moss as "Corso" on our Raza saved Emily in our universe, but their clearly more damaged AU Moss or AU Corso (if the switch never happened) voted to space her. So the fact they have the drive means she was there, the scene with AU Android at the end lets us know that Portia has/had skills (probably did the mods on Android, given she's thankful), and she or maybe AU Emily hooked it up successfully.
Otoh, looking at that, I realize we never saw just how damaged our universe's version of Moss was. We only got to know him as One. And his plan always sounded really stupid/cracktastic, so maybe that's because it wasn't his plan we were seeing/hearing about, but simpletonOne's assumptions about it. Ooo, this makes me happier. That was always a weak point for me, and it would be nice to see it fixed. (So, he didn't join the Raza to just kill Boone, but did so to get closer to the truth about who hired him, and schemes and stuff that hopefully made sense at the time. And probably then kill him, sure.)
This is not a thing.
Wait, no, you can watch too much SyFy, but not too much sci-fi.
* Dead horse: