I would do well to study the case of the revival of Hebrew as a secular spoken language in everyday life in Palestine, a little over a century ago.
It almost didn’t happen.
Initially, only a handful of thinkers believed this goal was possible, or even desirable, and only one man (Eliezer Ben-Yehudah), actually devoted his life to achieving it—initially, by using his first-born son as the first subject.
To this end, he and his wife spoke exclusively Hebrew to the boy, and shielded him from contact with other children and the entire outside world, lest he hear any other language that might ‘contaminate’ his mind.
The boy didn’t talk till he was four or five, and during that time Ben-Yehudah came under increasing pressure by friends and condemnation by society at large to succumb and allow the boy to hear the mixture of Yiddish, Russian, Arabic, Ladino and other languages that children in Jerusalem at that time heard in their surroundings. Ben-Yehudah stood his ground, however, and was rewarded with the boy calling him ‘Abba’ (‘Dad’) when he was five—and then started to speak in Hebrew.
After that, others were willing to follow—but only because Hebrew was crucial to the Zionist vision of national resurrection. Without that fervent ideological belief that hundreds of thousands, and then millions, of people subscribed to, it wouldn’t have happened.
It is highly doubtful you would have such numbers of people willing to make the effort to adopt Latin as their spoken language today, with its limited vocabulary and idiosyncratic grammar, if it is not integral to their national identity, and given that it there already are variants of Latin today that have been fully adapted to the terminology and needs of modern life—they’re called Italian, French, Spanish, Portuguese, Romanian…
The failure of Esperanto—which is an artificial Latin-based language, designed to provide a common denominator—to be adopted on a national scale is evidence of this.
(Originally written in reply to a question at Quora.com).