A discussion that comes up a lot nowadays when discussing the preservation of 'purebreeds' is the idea of outcrossing, or an open studbook. This is especially true when dealing with rare breeds that have very small gene pools (and genetic issues for instance). So, I thought I'd explain why that is very unlikely to happen here in Japan.
Also the breeds are officially designated as national treasures. The term is actually 'tennen kinenbutsu' which would translate to 'natural monument'. It's a designation given to wildlife and fauna that is native and particularly valuable to Japanese culture. This is something along the lines of say a national bird like the bald eagle in the US. You can imagine the uproar if it was decided to start breeding them with a Chinese eagle to increase genetic diversity. Trump might have something to say about that.
All jokes aside, there is an issue we have here in Chiba prefecture where the native macaques are interbreeding with a non-native introduced species, the rhesus monkey. There's been a lot of discussion about this because they've now reached a wildlife park where the monkeys are 'tennen kinenbutsu'. They've immediately put a cull in effect because basically hybrid offspring are no longer a native species, and so lose their official designation as a national treasure. I believe this same thinking would probably be used in any discussion regarding opening the studbooks for the Japanese breeds. NIPPO works closely with the Japanese government, always has, because of this official designation that the breeds have. The awards given at the grand national for best of breed are from the education minister, and the best in show is from the prime minister.
I realized that from an outside perspective it may seem that there's just a bunch of conservative old dudes shutting down new ideas, and to a certain extent there is that happening, the Japanese breeds have a lot more going on because of their official status.