The mods on this thread answered the OP's questions on multiple occasions. We aren't the ones trying to subvert a thread on Pluto into an assault on another school of astrology, using Pluto as a pretext.
Just to re-cap one point about rulership:
The hypothetical Pluto rulership of Aries is just a smokescreen. The only astrologers arguing this way on this thread are the neo-conservatives who wouldn't use Pluto as the ruler of Aries either. Apparently they enjoy this sort of confusion.
The Aries thing was based on the notion that:
(a) In Ptolemy's rulership system, the planets are arrayed according to their distance from the sun and moon (and summer solstice), in the following fashion (read the left-hand column down, and the right-hand column up to get the idea):
sun=Leo.....moon=Cancer
Mercury= Virgo......Gemini
Venus= Libra.........Taurus
Mars= Scorpio........Aries (then here we start over)
Jupiter=Sagiittarius..Pisces
Saturn=Capricorn...Aquarius
(b) Saturn was the outermost known planet prior to the discovery of Uranus,
(c) Uranus was beyond Saturn.
(d Capricorn and Aquarius both have Saturn as the traditional ruler, but the structure of Ptolemy's planet-sign rulerships could be kept intact if Uranus were assigned to Aquarius. The few Anglophone astrologers remaining, pre-modern astrology, tried to fit Uranus into the table of essential dignities early in the 1800s.
(d) Uranus did turn out to be a good fit with Aquarius, though not for the reasons initially postulated, namely that it was a malefic more or less like Saturn except more unpredictable. (There is a long thread over at Skyscript about this history.
http://skyscript.co.uk/forums/viewtopic.php?p=86611&sid=7d4a60429fc87410408c06c5047a03fd)
(e) After Neptune was discovered in 1846, (during astrology's Dark Ages,) it had no rulership. During the late 19th/early 20th centuries, astrologers began to work on its astrological qualities and characteristics. Sometime after 1900, the Neptune rulership was adopted-- if you read Alan Leo's books, he shows an interesting evolution from simply finding Neptune-Pisces affinities to a more solid relationship. Somebody must have seen a Saturn/Capricorn, Uranus/Aquarius, Neptune/Pisces logic, but that didn't seem to be a key reason for one of the fathers of modern astrology.
http://skyscript.co.uk/forums/viewtopic.php?t=8566
(d) After Pluto was discovered and named in 1930, some astrologers made a case for an affiliation with Aries, not Scorpio-- but interestingly, often based on its
perceived attributes (very modern!) as much as on its rank-order in Ptolemy's rulership scheme. (See Anton Jaks,
Astrology Handbook, 2010, p. 22, available as a google book.)
Jaks decried the switch to Scorpio as based upon similarities between mythological Pluto, god of the dead, and the 8th house as the house of death, with Scorpio as the 8th sign. On the other hand, astrology was in full tilt prior to Ptolemy's system of rulership, with clear mythological associations between planetary gods and signs long before he developed his scheme.
My personal feeling is that the neo-traditionalists aren't going to use Pluto regardless, so it shouldn't make a bit of difference to them if other misguided souls go off and do their own thing. However, they do love their game of "Gotcha!" moments.
Further, we now know that Eris, a trans Neptunian object, is a dwarf planet (discovered in 2005) that may be larger than Pluto. Mythologically Eris was Mars's (Ares's) sister, and likewise was believed to cause a lot of strife. Once more is known about Eris, she might be a decent fit with Aries. Astronomically, Eris's inclined orbit sometimes puts it closer to the sun than Pluto, so it isn't an utter mismatch for lovers of Ptolemy's system of planet-sign rulerships. From Wikipedia:
"Unlike the eight planets, whose orbits all lie roughly in the same plane as the Earth's,
Eris's orbit is highly
inclined: It is tilted at an angle of about 44
degrees to the
ecliptic. In about 800 years, Eris will be closer to the Sun than Pluto for some time."
Intriguingly, Eris's orbit is so tilted that it often appears against non-zodiacal constellations. To paraphrase Dr. Seuss, maybe astrology is ready to move
On Beyond Zebra.
The more we learn about asteroids and trans Neptunian objects, the more we can explore their astrological significance-- if any.
The above scheme doesn't fit identically into Ptolemy's, with Pluto still out-of-line; but then, modern astrologers can honour our traditional past without feeling straight-jacketed by it.