Here's a little something I found about a couple of examples of cross-breeding.
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"In dogs, closed registries and a ban on crossbreeding may be the rule, but the rule is not universal. Under the right circumstances, even major dog registries can accept crossbreeding.
About fifteen years ago a researcher crossed a pointer with a Dalmatian and then back-crossed to Dals in subsequent generations. He successfully met his goal of eliminating inherited urinary problems that are present in almost every Dalmatian. The board of the breed club petitioned AKC to admit some of the products of this breeding program � dogs which had only one Pointer in a five-generation pedigree full of Dalmatians. Two of the dogs were admitted, but the breed club�s membership raised a hue and cry, voting to rescind the request. AKC refused any further registration of the �cross-bred� dogs.
The membership of the breed club rejected these dogs because they were often mis-marked, allowing a cosmetic problem that might have been corrected in subsequent generations to take precedence over the elimination of a significant breed health problem.
Another crossbreeding effort received a registry sanction � this time from the Kennel Club. The English registry is at least as conservative in its practices as the AKC. Another scientist wanted to create Boxers which did not need to have their tails docked. He crossbred to a Corgi. (The bobtail gene in Corgies is different from that in Aussies and does not produce serious defects.) After five generations he had Boxers that looked like Boxers and produced like Boxers but had naturally bobbed tails. Those dogs were allowed to be registered."
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Here's the link...
Australian Shepherd Health & Genetics Institute, Inc.
This article is primarily about Australian Shepherds, but the same logic could be applied to any breed with endemic health issues. If a given problem can't be solved within the breed, going outside the breed can be a viable option.