As an astrologer I've developed an ambivalence toward the modern planets, and since discovering the re-emergent astrological tradition I've tended to push them into the background. Crowley discussed his take on them in The General Principles of Astrology (with thoughts on Pluto added later by editor Hymenaeus Beta), but didn't touch on Tree of Life or Book of Thoth correspondences because he was ghost-writing for populist astrologer Evangeline Adams.
I've had this debate with myself for decades now (nobody else in these parts to discuss it with); where do we put the modern planets on the Tree? For me, Crowley didn't quite nail it. My working hypothesis has been to put them on the sephirah but not on the paths, nor do I see a need to assign them to the cards as the elemental Fire, Water and Air attributions are perfectly serviceable. A few things that make me wonder:
Pluto I can see as Fire (since hypothetical planet Vulcan is still sitting on the sidelines with hypothetical planet Niburu, and the so-called Uranian or trans-Neptunian hypotheticals have drifted into obscurity). I agree that the best fit seems to be with Kether as it sits directly above Tiphareth, and I read a "Sun behind the Sun" (and "Son") analogy somewhere a long time ago. Although its modern rulership is Water-sign Scorpio, there is much of a "banked fire" character to that sign, and some astrologers have Pluto as exalted in Fire-sign Leo as well.
Since we are considering modern astrological theory and Uranus has been tagged as the "planet of astrology" as well as ruling Air-sign Aquarius, why shouldn't it be paired with the "sphere of the zodiac," Chokmah? Furthermore, Uranus was "Father Sky" in ancient Greek literature.
Although qabalistic thought describes Da'at as a "non-sephirot" (or at best a "concealed" one - is that Niburu I see peeking out of the closet?
), it would seem to be a perfect match for nebulous, mysterious Neptune, modern ruler of mystical Water-sign Pisces.
Just my 2 shekels' worth. Although working out potential correspondences is interesting (I do like Aeon = Pluto, although the latter has been "shrunken" in status now) I have no particular stake in any of this since I don't see the need for it. I suppose, though, that "nature abhors a vacuum . . ."