The Primer doesn't work without human sacrifice. It actually needed two special people: one without anything, and one with a powerful but unfulfilled nurturing instinct. It was a pretty unlikely confluence of circumstance that made it work, and Stephenson hints at this in the book. In fact, Nell is in some ways the perfect synthesis, the maximum amount of work (force over time) that could be created between the Vickies and the Anarchists, exploiting the order/chaos tension that is explicitly discussed in the last chapters. The Vickies know they are stable and creatively dead, and that this is an existential flaw.
BTW the r'actor giving up her career, and in many ways her life seemed strange and unlikely when I read the book long ago. But now, after kids, it seems realistic, especially because it satisfied her need to nurture.
Yes, Nell's character growth and arc was completely reliant on Miranda having a parental instinct and Nell being a child on a fast track to RAD before the TYLIP. The story about her character is absolutely about finding a human that loved her, through an unlikely mechanism. I just take issue with the idea that TYLIP's story is about how a human touch is needed for the concept to work, because as far as I remember that's not the case. That's Nell's story, not the Primer's.
BTW the r'actor giving up her career, and in many ways her life seemed strange and unlikely when I read the book long ago. But now, after kids, it seems realistic, especially because it satisfied her need to nurture.