I love this thread!
Just adding to the mix:
1) Expanding on your cardinal virtues idea, when I look down this row w/ 02, 05, 08, 11, 14, 17, 20 it really does seem like the separation of Virtues into every 3rd position could have been intentional as you pointed out, &/or at least in the Marseille ordering. But is it also possible that this schematic could have been originally intended to show more than just the named Virtues, but even to imply ALL 7?
02 Popess = Prudence(?)
05 Pope = Faith
08 Justice
11 Fortitude
14 Temperance
17 Star= Hope
20 Judgment = Charity(?)
2) Also, what if this 3x7 division could also show Cardinal, Fixed & Mutable groupings? These two rows look like interesting candidates anyway:
Row 1: Fixed Signs/Planetary Rulers
01 Magician = Venus/Taurus (thinking of Erhard Schon's 2nd House)
04 Emperor = Sun/Leo (King = Leo)
07 Chariot = Mars/Scorpio (Mantegna's Mars Card)
10 Wheel = Saturn/Aquarius (Schon's 11th House)
13 Death = Mars/Scorpio
16 Tower = Saturn/Aquarius (Lightning?); or Mars/Scorpio
19 Sun = Sun/Leo
Row 3: Cardinal Signs/Rulers
03 Empress = Venus/Libra; or Moon (as counterpart to Emperor Sun?)
06 Lovers = Venus/Libra (Schon's 7th house)
09 Hermit = Saturn/Capricorn? or Moon/Cancer (Schon's 4th house Hermit)
12 Hanged Man = Mars/Aries? or Venus/Libra (7th house of open enemies)
15 Devil = Saturn/Capricorn
18 Moon = Moon/Cancer
21 World = Saturn/Capricorn (MC?); or Mars/Aries (ASC?)
Some cards appear to align with this better (maybe) than others, but it's still fun to consider in context with Dangerdork's interesting re-division of the Majors. Cool stuff!
cbfdoll