Major Spoilers for all Expansions - Some general things I didn't understand

[Cleretic]

As the main thing unaddressed, I'll talk about #4:

The Omicrons are essentially bringing the records of people back as hard-light holograms. There's significant limitations to this--they can only do that to people that they have some sort of record of (which narrows it down to basically just 'Ultima Thule/Dead Ends denizens'; worth noting that they couldn't get the Nekropolis' people which gives you an idea of those limits), and there's likely some other limitations that we're not aware of because that doesn't really come up in the story. We know they can eat, and that they have enough sense of self and emotional presence to manipulate dynamis, and that's... well, kind of it.

They also don't simulate a lot of people. The reason why there is inconclusive, but I can think of at least two good reasons: either they only have finite capacity for creating those people, or--I think the more narratively compelling reason--they correctly recognize that all of the Dead Ends' civilizations would cause major problems if brought back en masse: The Grebuloffs are probably the safest but still have an incurable disease, the Karellians were at war and are still mad enough about it that it took being talked down for even just two of them to not kill each other, and the Nibirun are only relatively safe because they didn't have enough numbers amongst themselves to reach and enforce their 'everything should die' consensus.

But ultimately, everyone they bring back are simulations, not the original. They're real enough to be a person for all relevant intents and purposes in the Last Dregs, and they can learn to move on and live their own life free of the problems that brought the original to their end, but nothing suggests that we're actually looking at the real person. If you brought some sort of crystal containing all of Haurchefant's information (already a big ask, I don't know how you'd do it), and then convinced the Omicrons to simulate him (probably less of an ask, but still one), it wouldn't be Haurchefant: it would be a very convincing simulacrum, but it wouldn't be the real person. The dead guy is still dead, you just made a doll of him.

EDIT: Actually, now that you mention it, yeah the Last Dregs were absolutely populated by the same method that was used for the Omega raids. They're a little bit more real because at least the people in the Last Dregs certifiably existed at some point, but they're still just simulations, albeit pretty robust ones.