Yes you could. If you were a parent you would do it without blinking.
I don't know a single parent who would kill an innocent person to bring back a child.
And, since it appears to be Kes's plea to bring back her lover (and Janeway's desire to have Kes avoid the grief she & the rest of the crew feel at being separated from their loved ones) that helps Janeway to the final decision, I can state categorically:
I could not and would never even consider killing someone to save my sweetie.
Perhaps, in the view of people here, that means I didn't love him enough.