It's always been a mystery to me as to why catholic churches don't allow us to plug in our recorders into their PA system. Unfortunately audio is just as, if not more important than picture.
I urge all clients to be explicit to any church that their have a videographer that request access to their PA system to record audio from the various mics on the alter.
This simple request than make a profound difference in your wedding ceremony video. Its not always easy, but all clients should insistent to the church that this is something you require to get the most of their wedding video investment.