How in the world is it "defunct"?
Even in conservative Russian circles the holy fool is viewed as something from at least three centuries ago. The archetype may continue to appear in literature or film, but it is not considered part of contemporary Orthodoxy. Someone trying to revive it will probably have some problems with his bishop.
Anyone actively seeking to be a "Fool-for-Christ" will have problems with his bishop, but the same is true if someone actively seeking martyrdom too. Neither is because of such people don't exist anymore. Those who are called Fools-for-Christ or Holy Fools are done so after their death, and usually by popular acclaim.
As for the claim that holy fools are from "at least three centuries ago", here are some people from the past two-hundred
years who are acclaimed as Fools for Christ, and are canonized, or else considered righteous and listed in calendars on the day of their repose:
Blessed Anthony Alexseevich, Fool-for-Christ of Zadonsk (+September 29, 1851)
Anthony Ivanovich, Fool-for-Christ of Valaam (+June 7, 1832)
Asenatha of Goritsky, Fool-for-Christ (+April 19, 1892)
Blessed Athanasius Adrewyevich of Orel, Fool-for-Christ (+April 12, 1967)
Priest Peter, fool-for-Christ of Uglich (+Sep 3, 1866)
Blessed Schema-hieromonk Theophilus, fool-for-Christ of the Kiev Caves (+Oct 28, 1852)
Anthony Ivanovich, fool-for-Christ of Valaam (+Jun 7, 1832)
New-Martyr Michael, Fool-for-Christ (+Apr 1, 1931)
Blessed Parasceva "Pasha of Sarov," Fool-for Christ of Diveyevo Convent (+1915)
New-Martyr Theoktista Michailovna of Voronezh (+Feb 22, 1936)
...and also consider that St John the Wonderworker of Shanghai and San Francisco (+1966) has been called a Holy Fool by quite a few people.
One of the defining things about Saints who were "Fools-for-Christ" was that they were mocked and thought insane: i.e. just fools. I inwardly wince at your comments for the simple reason that those who mocked the great Saints in previous centuries also thought the yurodivy
to be not "part of contemporary Orthodoxy". I think it's too strong a statement to say that such a calling doesn't exist anymore. From the witnesses of the Church, it seems once a particular podvig
appears and flourishes, it never entirely disappears again*.
The possibility of it is always there, because it has been revealed as path to Salvation.
*monasticism is a great example of this, which grew t the time of St Anthony the Great, and has never disappeared since