So too with the idea that the Chronicles would each be tied in theme to one of the medieval planets of both astronomy and astrology - the five visible planets plus the Sun and Moon. Lewis explicitly tied his Perelandra series to the planets in both their physical and mythological forms. Why not the Narnia books as well?
Unfortunately for those who like to see behind and underneath things, neither is likely to be true. Lewis’s own words are available to give the disproof.
Some people seem to think that I began by asking myself how I could say something about Christianity to children; then fixed on the fairy tale as an instrument, then collected information about child psychology and decided what age group I’d write for; then drew up a list of basic Christian truths and hammered out ‘allegories’ to embody them. This is all pure moonshine. I couldn’t write in that way. It all began with images; a faun carrying an umbrella, a queen on a sledge, a magnificent lion. At first there wasn’t anything Christian about them; that element pushed itself in of its own accord. Of Other Worlds
I think I agree with your order [i.e. chronological] for reading the books more than with your mother’s. The series was not planned beforehand as she thinks. When I wrote The Lion I did not know I was going to write any more. Then I wrote P. Caspian as a sequel and still didn't think there would be any more, and when I had done The Voyage I felt quite sure it would be the last. But I found as I was wrong. So perhaps it does not matter very much in which order anyone read them. I’m not even sure that all the others were written in the same order in which they were published. CS Lewis’s Letters To Children
We could, of course, line them up with whatever group of seven we choose. If we wanted to line them up with the characters from Gilligan's Island, we would have Mr. Howell for Voyage of the Dawn Treader, Ginger would go with The Silver Chair...