Tobias,
If we use a person object as an example, this person object can be referenced for example by an admin-c or tech-c attribute at the moment.
In future it can be referenced by the abuse-c as well, BUT to create this reference the person objects needs to have an abuse-mailbox attribute. If there is no abuse-mailbox attribute it can not be referenced by the abuse-c. This will be done by the business logic.
I am confused because i remember the discussion slightly differently and this is also not in line with what the policy proposal text says. We should not overlay existing objects with magic that does or does not make them eligible as a target for a reference. Also, abuse handling is more or a role function, so if at all, we'd talk about a "role:" derivative here. Some gatekeeping is indeed advised.
Same when you query for an ip range - admin-c, tech-c and abuse-c can be the same person, but output will show an abuse-mailbox attribute in the abuse-c part.
This could be misread as giving different views onto the same object depending on the reference that made it appear in the output. -Peter (usual disclaimer applies)