I'm not prepared to believe that very many people have come to Christ because "prophecy proves the Bible." To begin with, Christians who believe that kind of thing are a small minority of Christians as a whole. How does it work? You prove that the Bible is "true" by OT prophecies so then you have to believe the Gospels are true and if the Gospels are true then you have to believe in Jesus?
Well hmmm lets see..
=================================
Christianity Today seems like a good place to start.
2015
Adventists: Can Ben Carson's Church Stay Separatist?
"In 2014, for the 10th year in a row,
more than 1 million people became Adventists, hitting a record 18.1 million members. Adventism
is now the fifth-largest Christian communion worldwide, after Catholicism, Eastern Orthodoxy, Anglicanism, and the Assemblies of God."
===============================
And then there is USA TODAY -
2011
Adventists' back-to-basics faith is fastest growing U.S. church - USATODAY.com
"
Adventists' back-to-basics faith is fastest growing U.S. church"
"Newly released data show Seventh-day Adventism growing by 2.5% in North America, a rapid clip for this part of the world, where Southern Baptists and mainline denominations, as well as other church groups are declining. Adventists are even growing 75% faster than Mormons (1.4 percent), who prioritize numeric growth.
For observers outside the Seventh-day Adventist Church, the growth rate in North America is perplexing."
=============================
So how are they doing that?? well they do it using the very method you say in your post that you can't imagine being used.. to do that very thing. -- They start by showing that the proven predictions of the Bible - prove that the Bible is inspired by God.