what fun!

as an AI researcher I have thought about the replacement you discuss. Your take on how it is managed is interesting… I have thought of this marriage as you call it too. in general it seems that the speed of our brains (even simulated) will be many orders of magnitude slower than that of our AIs, so the idea that we (as humans) get to operate w. them always seemed implausible. BUT your idea of marriage is interesting, perhaps the child would still seem human even if it was also something much more at the same time.

Even if we are to manage such a thing, I suspect that most today would still view this is the death of humanity.

(but rectangles thru space seems wrong… they will travel as info not as matter… speed of light separation is interesting, and seems right. but I have a feeling that they will not be unitary in the way that you are I are. After all if I clone 3 of me and spend 1 month in 3 different places, I am now kind of three different people…. but not so much. I would probably willingly remerge. but I would NOT merge w. a random person, that would be like death. So notice that the very idea of separateness becomes blurred in that world. Still I love your piece!)