Ashes to Ashes was not a Kim episode. It was about the reality of death. Kim was just there to dramatize that the best you can hope for in the end is to say goodbye. And Mezoti showed up at the end because the young always continue to live their lives after others die. No doubt they would have preferred Paris to have been the lover but he was taken by Torres. The only unattached male of the right species was Kim.
And I strongly suspect they wrote a new dead character because they didn't want to call back a glorified extra. The thing is, it doesn't matter if Ballard was previously obscure because in truth many lives go unnoticed and unremarked and only after they are gone do we (sometimes) notice we've lost something.
The key scene in Ashes to Ashes is when Janeway cannot justify her decision to the dead. This is true for all military commanders whose soldiers die following their orders. The implicit lesson? It's left for you to draw.
A fair amount of Voyager is this kind of story. The insistence on some sort of survivalist epic crossed with a right-wing critique of humanitarianism is just irrelevant to what was on screen. It's like people keep watching the insides of their foreheads.