I think I understand your position much better now, thanks for the clarification. Let me get some quibbles out of the way before we proceed.
First, I think you're missing the point here in your responses. It's not that the incarnation "cannot be thought" in a literal sense, as if no idea of an incarnation can enter our minds. The point is that it cannot be understood or comprehended by the human rational capacity. If we don't see why this is so, that is only because we are too familiar with the idea.
Climacus makes mention of different ideas of an incarnation of the god. The first is the old Greek conceptions in which the gods walked around on earth "disguised" as humans, so to speak. They weren't really and fully human, however -- it's more like they were wearing a "human suit" and a perceptive eye could pick them out. This is an aesthetic form of belief.
The next is pantheism, associated with RA (or the aesthetic sphere) in Climacus's thought, in which everything is essentially god and the appearance of difference is illusory, so we seek to annihilate appearances in order to see the eternal behind everything.
The point of these two rival notions of the incarnation is that they involve no contradiction. In the old Greek conception, the gods aren't really human, but appear human--so no contradiction. In the pantheist conception, the appearance of human individuality is illusory, invalidated, so no contradiction.
However, in the Christian conception, we have the paradox of Christ being fully human and fully Divine simultaneously, even as an infant. Yes, we can "understand" this idea -- but we cannot understand how this is possible. From a point of view that demands rational consistency in language use, it's frankly ridiculous. That's why only Christianity presents the paradox and why only Christianity can present the paradox, in Climacus's opinion.
Now, as I understand your thesis, you believe that Climacus, yes, presents stages, but doesn't -rank- them, correct? In that case, they're not really stages at all, but simply spheres of existence, and there's no point saying one is more advanced in any sense than another? I think this represents one of two very different readings of Climacus (stages as progressive stages and stages as spheres), both valid, but I think the point here is not that we choose one or the other, but that both are simultaneously true.
To see this we need to keep in mind what Climacus said on the very first page of CUP -- the question before him is what it means to become a Christian. He understands this to be the most serious question imaginable, as it has to do not just with our temporal happiness but our -eternal happiness-, and is therefore -infinitely important-. I don't think this is jest, nor is this element of his book a curious thought experiment to which he attaches no ultimate importance. His thinking has a goal in mind -- so that means a trajectory has been set, and Christianity is the final stage of the trajectory. To the extent that Climacus calls this activity a thought experiment, he means it in a self-effacing way: he is not qualified to definitively state what it is to be a Christian as he is not one, but an RA personality.
So while we are within any one stage, the stages are spheres, but as move through them toward Christianity, the stages are stages.
The point is that the importance of the stages as stages, to us as readers, ultimately depends upon whether or not Christianity is ultimately true. If it is not then these are all just equally valid options. If it is, then there is a definite goal in view, and once we reach it everything beforehand were stages on life's way.
I don't think there's any question where Kierkegaard sided in all this, as his signed works were religious and he considered entering the pastorate until late in life.
But that doesn't mean there's no question for his readers.
Kierkegaard's point is that our reading of Kierkegaard involves a self-defining choice. This is made possible by the pseudonymous nature of his works.