Yes, I have read what he said about elliptical. In fact, this is my 2nd read-through. But keep in mind that there has been research done since this book was written. Even Prandtl himself, that developed the lifting line theory, later on stated than bell-shaped was better than elliptical. And the Hortens also used bell-shaped, at least in their later designs. This, for some reason, has been practically ignored. And Nickel himself states several times in the book that you will never get perfect elliptical, only "good enough" (whatever you want that to mean). As for morphing, I remember one idea where the wing tips were sliced like a loaf of bread and then covered with a flexible membrane. The slices are mounted on a tube running span-wise. Only the very tip slice is fixed to the tube, and the tube is then rotated to get different twists.