Having worked on a pet food stall/pet shop for more years than I care to admit, I would say that the only way to do something like this would be on line, as most people can't even remember what food they feed their dogs, let alone spend the sort of money this would cost. 'Professional' dog people (breeders, show exhibitors, agility/obedience people etc) tend to stick to what they like and the only people you would attract would be those that can afford to spend a good deal of money and don't want the hassle of preparing their own 'healthy' food. Personally I can't see much of a future for it, but wish you luck anyway!