COOL IDEA, LOVE IT!!!
I wonder if "positive only" training would be more clear to the viewers, than "clicker or voice based" training, if "positive only" is what you meant? ("voice based" training, may, or may not be, positive only, depending on that person's ideas of what "voice based" training includes...).
and i think cuz of the "pull a buggy or cart" you might lose a lot of contestants, cuz few of us have carts or buggies...or dogs big enough to pull a cart.
OHhhh, wait---do you mean, this is a contest for HUGE dogs, or a huge contest for dogs?
do the dogs have to do ALL the tricks you list?