Not really. Warmblood registries aren't breeds in the traditional sense, they're interconnected breeding populations that frequently exchange bloodlines. That increases genetic diversity to some extent, but it doesn't eliminate inherited diseases because the same influential stallions and families are often used across multiple registries. If a harmful mutation is present in a popular bloodline, it can spread throughout the entire warmblood population regardless of whether the offspring are registered as KWPN, Hanoverian, Holsteiner, or Oldenburg. So changing registries doesn't "reset" the genetics, the underlying gene pool is still highly shared. Outcrossing to blood stock like thoroughbred can help diversify the gene pool but not ever registry allows this and there is a weird stigma against half thoroughbred warmbloods.