YOU want to do large format shots. What about the bride? I used to shoot weddings for the $$ and I have to tell you nothing would be more annoying than some amateur rolling up with a large format camera. Leave it at home and go enjoy the day. Take a small camera if you want and take candid shots. Don't interfere with the pro. He was hired for a reason.
Ditto. A wedding is already stressful for everyone involved, and what you are proposing will just add more stress.