Thanks, Amy, but I decided to punt on the idea of setting it in the future. Too much effort just to try and justify why the Antichrist is going after the Catholic Church. It's the Mother Church. No greater reason needed. The Omen series totally ignored 95% of Revelation. I can skip a few signs of the Second Coming, especially since no one seems to agree on which are real signs and what they mean.
However, I'm considering including a female detective in the Gendarmerie Corps of Vatican City State who investigates a series of disappearances and murders among priests, bishops, and cardinals in and around Vatican City, which is a sign of the Antichrist at work. How does Detective Amy Ess sound? There're actually only 130 people in the Corps, and, knowing the Catholic Church, they're probably all men, but what the hell. I want at least one major female character in the book. There will also be a possessed reverend mother, but she will probably only appear in one chapter.