I believe I'd keep a dog that didn't hunt. By the time you know if it is going to hunt or not, aren't you usually attached to the animal? I guess I don't get dogs "just" for hunting, though all of my dogs are bird dog breeds.....maybe I shouldn't have responded to this question I guess b/c I've never had a dog that wouldn't hunt. I had one dog that was gun shy for the first 2 years I tried to hunt her. Persistence paid off and she's now the leader of our kennel and I've enjoyed 10 good years of hunting behind her.
When you refer to a dog that won't hunt, do you mean it is not interested or is this related gun shyness? Is there a GSP, GWP, or Brittany in the world that isn't at least interested in the pursuit of live birds?