It's a good thing O'Brian was on Deep Space 9 and Janeway was in the Delta quadrant, or the federation would would have turned into a STARBUCKS with 2 remaining employees (one of whom is in the pattern buffer).
Yeah, given how the technology works, the only reason they can't just save a copy of everyone to reconstitute later if something unexpected happens is the handwavium compensator.
That's what happens, though, as proved in that Riker episode. He never left the planet, and a clone was created.
You only feel like you because your brain contains your memories. We could secretly clone you atom by atom and kill the original, and no one would be the wiser. Not even you. The new you.
In "Old Man's War" they explain their mind uploading to a new improved body by a short moment where you feel like you're in both bodies at once. Basically if you can synchronize both consciousnesses you can terminate the old one without it feeling like your existence is ending, because you exist in two places at once. That's kind of what most episodes about the transporter suggest too, that you're conscious during the transfer, and consciousness exists outside of the "physical" world.
Since that's not possible in the real world, mind uploading would mean death too. The only way mind uploading can work for human minds is if you'd slowly alter the brain synapse by synapse (say over months or years) and slowly upgrade your brain and turn it into a computer without there being any determinable break in consciousness. You still couldn't beam your mind to Saturn and back at lightspeed though.
In The Culture series they address the problem of cloned minds send into android bodies that it's possible to reintegrate two consciousnesses back into one. But only if they both agree to it.
Janeway was given the option to murder a sentient, self-aware individual being in order to bring back her two dead friends. The ends don't justify the means.
It's the opposite of their ideals, but it seems real in line with their practices (with the possible exception of Picard who is some sort of scrupulous perfectionist at least after season 1)
What if you could save two of your friends by killing a sentien, self-aware alien that is trying to kill them? What makes their lives more valuable than random alien mook #49. In this case it's the justice and motivation that justifies the ends.
PS: And yeah it's still wrong to murder tuvix but very "primitive human" to sacrifice one to save their own tribe (see quark in little green men). But her real crime was insisting to return to the alpha quadrant instead of settling somewhere safe and build a second federation.
No one was trying to kill Tuvok and Neelix, they were already dead. Victims of a tragic transporter accident which unfortunately ended their lives, with the additional result of a completely different individual coming into existence. Which brings me to
Tuvix isn't a belligerent, he is a complete innocent. He bears zero responsibility for the manner in which he came to be, he simply exists and, like every other living, rational being, wishes to continue existing.
Janeway's actions were not a matter of defense of others by killing an enemy who was threatening them, they were a ritual sacrifice of an innocent as a dark offering to return her dead back to life. The fact that her means was technological rather that magical doesn't change the fact that she murdered an innocent person to bring back two people who were already dead.
a ritual sacrifice of an innocent as a dark offering to return her dead back to life
Haha I love that. It would have been awesome if Tuvix "mental energy" would have reappeared later to haunt the ship and take possession of various ship systems to kill Janeway. Mostly by coffee.