Aries is The Magician...
http://www.sacred-texts.com/tarot/gbt/gbt08.htm
The Emperor is Cancer
www.sacred-texts.com/tarot/gbt/gbt11.htm
What???
Maybe the people who created tarot cards simply had a different understanding of what makes an emperor compared to the creators of astrology's notion of emperors.
Those keywords you mentioned are attributed to Saturn, in the modern understanding of traditional astrology.
Furthermore, if we are talking about which planets represent emperors in the tradition, there are three. The Sun, Jupiter and Mars. Specifically, the Sun is considered to be the authoritarian and royal King who is good at making sound judgments. Jupiter is the popular, just and moderate King. Mars is the general King, brave, physically strong, and serious. These are the positive traits when the planet is well placed.
The negative traits for a Sun kind of King is egoism, narcissistic and attention-seeking. For Jupiter it is a King prone to excesses in food, drink and sexual relations. For Mars it is recklessness, violence and unstable behaviours.
So when we talk about Emperors/Kings, the question is, what kind of?
So a Sun in Aries is very authoritative, royal and of sound judgement.
The issue is the attribution of mostly but not totally Saturnine traits to the Emperor card, and then trying to connect those attributes to Aries simply because the zodiac sign associated with the Emperor happens to be Aries. Association does not work that way, in my opinion. There should be some overlap between Aries and The Emperor, but that does not mean that ALL of Aries's qualities should be present in The Emperor, nor vice versa.
Moreover, Aries's impulsive qualities is due to being the domicile of Mars, but I would like to propose a better reason for it to be associated with The Emperor, rather than simply because it is the "first sign of the zodiac", whatever that actually means. According to the Wikipedia entry, "the sign of the Emperor is associated with the sun sign of Aries". The important phrase here is "sun sign of Aries". This implies Sun in Aries represents The Emperor. This is more in line with traditional astrology, as the Sun is exalted in Aries. According to Maternus, an exalted planet is "raised up to its maximum power". So a Sun in Aries is very authoritative, royal and of sound judgement. The Sun is also the proper significator of authority figures, and The Emperor is a symbol of an authority figure. The Sun is no doubt, more powerful and authoritative than Mars or Jupiter, because without it, there would be no life.
And, at least from what I've noticed, most often the plucky protagonist hero would embody Aries: Impetuous, competitive, not-all-too-bright[, sometimes a bit hot headed, but good-natured overall. See Ash Ketchum from Pokemon, or the Red Ranger from Power Rangers (my age is showing haha).
The thing is, no one is really like any of these things. They are hyperboles. Tarot cards are also hyperboles... symbols... and considering the greater number of major arcana (and minor) to zodiac signs, I don't think there is a 1:1 ratio of correspondence between the zodiac signs and specific cards. There is also no specific set of characteristics possessed by one sign that make a good "emperor" or leader, imo, and since no one has just one sign influencing their entire chart, you can have a "disciplined Aries" depending on lots of things... even if the sign itself isn't associated with discipline.
According to a manuscript translated from the original Ancient GreekPerhaps we've been brainwashed by popular cultural archetypes of leaders to see them as one-dimensional beings that cannot simultaneously aries-like and cancer-like and capricorn-like and leo-like all at the same time, or perhaps signs not associated with leadership at all.
Growing up watching a lot of cartoons, it was interesting to note a change in the "type" of leader that was portrayed to young people. In ensemble cartoons, there is the "plucky hero" to save the day, the main protagonist who leads a group of other characters that all have their own roles. These roles are obviously made to be easily recognizable and shallow to allow the greatest amount of identification from the young audience.
And, at least from what I've noticed, most often the plucky protagonist hero would embody
Aries: Impetuous, competitive, not-all-too-bright, sometimes a bit hot headed, but good-natured overall.
See Ash Ketchum from Pokemon, or the Red Ranger from Power Rangers (my age is showing haha).
According to a manuscript translated from the original Ancient Greek
viewable at http://www.csus.edu/indiv/r/rileymt/Vettius Valens entire.pdf
QUOTE
The Nature of the Twelve Zodiacal Signs.
'…...Aries is the house of Mars, a masculine sign, tropic, terrestrial, governing, fiery, free, upward trending, semi-vocal, noble, changeable, procuratorial, public, civic, with few offspring, servile, the Midheaven of the universe and the cause of rank, two-toned (since the sun and the moon make white lichen). It is also unaspected and ecliptic. Depending on its relationship with the houseruler, men born under this sign will be brilliant, distinguished, authoritarian, just, hard on offenders, free, governing, bold in thought, boastful, great-hearted, restless, unstable, haughty, inflated, intimidating, quickly changing, wealthy. When the houserulers are favorably situated and have benefics in aspect, kings and powerful men are born, those having the say over life and death.....'
This sign is productive of order, earthy, rustic, related to farming, a freedman, downward-trending,
with few offspring, semi-vocal and mute, noble, invariable, energetic, unfinished, indicative of estates and
possessions. The ecliptic lies to the north, rising in line with its <Taurus’> highest point. Men born
under this sign are noble, energetic, toilsome, good at keeping things, pleasure-loving, music-loving,
generous. Some are laborers, propagators, planters. If benefics incline toward this place or if the houseruler
is favorably situated, men become priests and school superintendants, as well as those judged worthy of
crowns and of the purple, of monuments and statues; also supervisors of temples and distinguished and
brilliant individuals
P.s. Synchronously, flapjacks you mentioned the Scorpio type hero, and I think Darth MI's namesake and avatar - Darth Vader - is exactly a Scorpio hero archetype!