Ok, so I've just sent a PR for adding the private clearDefaultValidationProviderResolverCache() method. This will allow us to gather experiences with that functionality before committing to it on the spec level.

One other complaint that I have about calling private methods across components,

Understood; that's why I think we should remove this down the road in the favor of a truly portable approach. It's too late for adding it in the scope of 2.0, but we can explore it using that private API now.

describing the clearValidationProviderCache() method in some HV documentation

That's good idea.