IMHO this situation was not morally ambiguous, like at all. There was a transporter accident. Two crewmen died. That's that. The fact that a new sentient being came to life as a result is a completely separate matter. That being (Tuvix) as far as anyone should be concerned, was a newborn.

At that point, what you had was a tragic accident of no one's intention or volition.

The choice was never "save two crewmen" vs "save Tuvix," because at that point, the two crewman were already dead. And Tuvix was alive and in no danger. There was no moral impetus to do anything. A tragedy happened, it sucks. Move on with life.

So IMHO Janeway absolutely, intentionally, volitionally murdered Tuvix, who was a newborn in no danger. She absolutely resurrected two crewman who were already dead. She did this for her own personal reasons, and acted immorally. QED.

Thank you for coming to my irrationally-important-to-me TED talk.