There were some rumors, that the youngest Magus was presented by the young Lorenzo himself. There are better documented statements, that in the Pope-Pius-Trionfo in April 1459 Lorenzo (10 years old) had some engagement with his "banda" (his friends) at this opportunity, somehow as part of the show.
I'm pretty sure the consensus is that the young magus is simply an allegory of Medici dynastic succession - the whole painting, apart from commemorating actual illustrious visitors to Florence under Medici rule, being a tribute to the Medici assumption of the annual Florentine procession of the Magi to San Marco (also controlled by the Medici).
Dynastic succession in the Gozzoli painting: Following the young Magi allegory, you have Piero taking the lead as he had assumed a leadership role by this date (but would be contested when Cosimo died), followed by the elderly and ailing Cosimo on humble mule (with his personal imprese
of a metal torch), then the young 9 year old scion, Lorenzo, further back whose head is found just above and between the condottiero
princes Galeazzo Sforza and Sigismondo Malatesta, sending the none-too-subtle message that the Medici dynasty is guaranteed by arms. In that very year of 1459 Lorenzo basically serenaded Galeazzo (who was looking down from Medici Palazzo) with an armeggeria
out on Via Largo, in which a famous triumphal float of Cupid accompanied the mounted 'knights', with Lorenzo at their head; thus political-military ties packaged into 'professions of love', etc. The much-discussed cassone (mistakenly dated to 1440 in most publications; see the relevant/corrective study by Patricia Lurati on academia.edu) of the joust in Santa Croce occurred during this same state visit from Galeazzo (hence the Sforza dog imprese
on the banner on the left).
I posted this above, but again there is general consensus that this is Lorenzo - the age fits perfectly for 1459 and his 'broken' nose is unmistakable:
At all events, why do the 'CVI' and 'AS' decks feature black shields on the highest suit of swords, a color of mourning?
My 2 cents again: The novel introduction of a male ruler on the Chariot was done in the 'AS' because Costanzo had just inherited his fief of Pesaro and the wedding with an Aragonese princess guaranteed the stability of his fledgling rule. The 'AS' king of swords has a black shield because it commemorates Costanzo's illustrious father Alessandro (who errantly gives his name to this deck), deceased just two years prior (and whom first acquired Pesaro for the Sforza). A few years later the Pazzi Conspiracy happens and then the CVI; the slain Giuliano commemorated in the sword court cards, also with a black shield (not king, naturally, as he was not the senior brother), according to my view.
I would also argue that the Sforza had already been commemorated with a deceased paternal figure in the King of Swords in the CY, Muzio Attendolo Sforza, who famously died drowning in his armor trying to save his page who had fallen into a river (who would have cared for the helmet and arms not being used) - and sure enough, a single page with helmet on is in this card, and the Sforza device of the cotogna
is the imprese
on the chest, symbol of the dynasty's hometown of Cotignola (symbolized by the mela cotogna
A 20th century imaginative painting of Muzio's death (which merely speaks to the well-known manner of his death):