This emphasis on Isaac being the miraculous child through which God's covenant with Abraham will be fulfilled is how the story was approached by most of the preachers I heard growing up (though you've expressed it more eloquently). And I think the story works well enough if we hear it in that way. God makes a promise to Abraham, and gives Abraham a magical thing through which the promise will be fulfilled, but then asks Abraham to give up the magical thing, because Abraham's trust should be in God alone and not in any particular magical thing. That's a pretty good sermon.
Not to be a butt, but............I'm not sure that attributing the term "magical" to the story as a descriptor really conveys the locus of meaning in the narrative (whether the Akedah turns out to be a bunch of fiction, or is a story intended to be taken more, shall we say, essentially).
My main point wasn't to bring up a feature of context that we all already usually know. No, my point is to emphasize how we need to be reading the story, especially if it's presented in juxtaposition and in progressive manner to what came before it in the book of Genesis.
It was only when I became a parent that my focus of attention in the story shifted, because of course the "magical thing" is a child, and one of the primary moral duties of a parent is to protect one's children. That was the point at which I started seeing God's command to Abraham as monstrous -- not just a command that's difficult to carry out, but a command that's evil to carry out.
When we had our child, my focus in reading didn't change. I think some of how we read any text, whether it's a book or movie, or whatever expression of human communication we're receiving and attempting to decode, is conditioned by the earlier social experiences both good and bad that each of us has gone through.
At the same time, hermeneutics needs to be emphasized, because in the Akedah narrative, we all also know already that what is being asked of Abraham is wrong. And why do we know this? Because we were raised in a Western democratic society with notions of Human Rights pumped into us day in and day out? Partially, but not only from that because we see in the narrative the earlier instance of Abraham arguing with the Lord over sparing the innocent in Sodom and Gomorrah and that it wouldn't "befit" God to do something heinous.
(Note that I'm not talking about being overprotective. Parenting is a complicated balance of many things. But, as our moral duty, we protect our children from starvation and disease and people trying to murder them.)
Yes, that is the case, isn't it?
Sometimes when I'm reading a book or watching a movie with my family, and something implausible happens (like, how do they have gravity on that spaceship, or why don't the Hogwarts wizards use time-turners and luck potions all the time when they're fighting Voldemort), we laugh and say "Don't worry about it, it's not that kind of movie." So maybe this story was like that to the ancients who told it. The storyteller is telling me a dramatic story around the campfire, and I'm getting distracted by side details.
Somehow, I don't think Paul thought of it in that way. But hey, there's a better way to excise this passage by applying the Documentary Hypothesis or other intensive Critical studies of the Bible. If we want to do that.
We can also choose to think that because it seems fanciful in its awefulness, it must be a "fireside chat." Or we can apply some moderate historiography and consider that even if the story is legendary, it might be conveying an
inverted precedent----------------that is, that God, by asking Abraham to prove his faith, also, at the same time, set up a typology of salvation AND.........AND..............established the point that God is never going to ask anyone to sacrifice their own children. (And I don't care what some folks think they find in Ezekial to the contrary).
The point is, the Akedah was a purposeful one-off event, to set up a pattern of meaning for the future, culminating in a fulfillment by Christ.
Now, again, I know I'm just preaching to the choir. You're a highly educated sister, and I realize that. But it seems that too many folks these days all too easily adapt and impute to the biblical text their own "reader-response" interpretation because..............well, we now live in a postmodern and socialist leaning world where everyone can no longer bring in the heavier consideration of Philosophy. And I always put Philosophy and all of its environment (Hermeneutics, Epistemology, Historiography, Textual Criticism, etc.) before Theology.