The Tachikoma might have been the thing that interested me most by the end of SAC. I found myself empathizing with them as well, and feeling for them — I suspect, in the way Batou does.
One of the delicious things SF does, and SAC certainly does, is invite us to consider ideas we normally wouldn’t — usually for emotional reasons. I think we must at least consider the possibility that the Major is actually correct in her concerns, and that we, like Batou, are falling prey to the cute design and voice of the tachikoma units — what would it mean for them to read about human emotions? It’s possible they aren’t doing anything that’s outside their programmed parameters.
The existential quandary of a created lifeform is as old as Frankenstein, of course — and older still, since it’s the primary concern of religion in the face of a creator deity — and SF uses robots, cyborgs, androids, and all sorts of things to play with the idea. It is possible that the tachikoma are practicing self-preservation, something they are programmed to do unless specifically “ordered” (verbally or through cockpit controls) to do otherwise. How much of their behavior, the show invites us to wonder, is actually a growth from an agglomeration of experience and data, and how much is simply geometric growth of AI responsiveness in the face of experiential data and problem-solving skills?
Now, I’m not actually claiming that’s correct, only that it’s an uncollapsed possibility in the text, lying alongside their growth and emotional development.
And as all things in the show do, this development reflects back on Kusanagi. If she is entirely mechanical, what is human in her besides the agglomeration of experience, emotional and physical? If most of our emotions are due to chemicals in our bodies, and she doesn’t have these things, what’s left for her? Is she afraid of the tachikoma because they remind her of herself? Intelligent, growing, learning, but unfeeling save for certain consciousness-patterned behaviors? Is she simply an AI based on the personality of a child that’s experienced years beyond placement in a mechanical body?