If it were possible to just clone the needed tissue - grow just a kidney, for example, I'd be fine with it. Otherwise, I do not think it will ever be actually done - clone a whole person just to harvest an eye or a spleen, despite many science fiction doom-and-gloom movies and stories to that effect. It is just too morally tricky.

And, to grow, for example, a kidney big enough to serve an adult would take years if you grew it inside a whole human ... same for heart, eyes, lungs, etc.

I understand this is for a paper, but I do not think the original premise will ever be morally acceptable to most of humanity.