I second the buying a backup camera. With two- you not only have a back up, you now have 72 frames before a reload, and/or you can have two different stocks loaded at one time. One black and white, one color....or whatever.
As for the batman utility camera belt idea- I've made one of those for my Bronica, yes you look a little strange (I ceartainly feel strange when I wear it) but it is nice to have.
And I dont know if they are still available now, but I remember seeing ads for formal dress vests that were made for wedding photographers. They were photo vests designed to go with your tux.
I'll second the idea of trying to get an F100 as a second body. When I did a wedding in similiar circumstances, I used an F5 for all the colour work, and an F2 for all the black & white. It was an outdoor wedding so I was able to switch cameras at will, and swap lenses between cameras. (I think I would have gotten confused if I used two identical bodies)
Whatever works for each photographer but when I used to shoot motorsports I always carried two Canon T90s. The idea was when the main body broke (never happened) I could switch to the backup without any hesitation or thought. After many events without any problems I ended up usually loading different films (or the same with different lens choices) in each and designating the different film type with colored tape.
Various Canons and Nikons. A Mamiya and a Bronica. A couple Brownies, and a Couple of Argus' (Argi?)