I would never, under any circumstances, breed a bitch who wouldn't breed. That's Darwin at his finest, screaming from the hilltops, that natural selection is alive and well. In the wild, she would not reproduce. Period.
Not that I disagree with you about the issue of breeding a difficult bitch, but you're incorrect that this is natural selection. These breedings would probably never even occur in the wild or who even knows how it would be structured were it left to nature. There would be different selection criteria and nature would truly be work when breedings occurred naturally in the wild with nature doing the selection.
We use artificial selection to breed domesticated animals. No two ways around it. We are already interfering and have interfered with nature to make these breedings happen. We play nature and select what we want. This entire endeavor is artificial and manipulated by human beings. Think about the grains that you eat or the fruits that you buy, this is all artificial selection at work. It's odd when we start bringing natural selection reasoning into a process that is already artificial because the entire process is already manipulated BY human beings, not nature. We have to decide just how much we want to interfere when we carry out artificial selection on our domesticated grain, fruits, vegetables and animals.
I've seen a small scale of how breeding would go if dogs were left to their own devices. I grew up in India, have seen the street dog packs and observed their reproductive behaviors. That is more akin to "natural selection". Nature decides which dogs get the best food, who gets to survive dog fights, who gets to escape from traffic, who gets to breed, who is strong enough to whelp a successful litter and which puppy gets to survive to adulthood.
When we pay a 1k stud fee, build a whelping box, give a bitch oxy, help a pup from succumbing to fading puppy syndrome or do any of the other myriad of things we do to interfere with domesticated animal breeding, that is hardly what I call "natural selection". Keep in mind that we are already over the top involved in the artificial selection of
everything domesticated.