Allow oneboxing within private categories

In our communities, which have extensive private categories, we are finding the limitations on oneboxing a bit of a problem.

It means that we can’t easily do nice internal linking in any of these categories. As these contain around 50% of our traffic, this is quite a limitation.

It would be great if we could onebox links from the same private category, or also from its parent category(ies) (which by design must share the same permissions).