There was some talk a while back that Privacy Rules would be updated so that you could test against the data in a sperate list. refer this post
For example, lets say I have: Users of type Teachers and Students, and I have another list called Classes. Classes has three fields: Class, Teacher & Students.
Students details are private unless a you are a Teacher in a Class with the Student, and then the Teacher is able to view the Student’s details.
Now, while I could put this data into the User data-type, this is only a simple example to illustrate what I’m talking about, so please don’t tell me how to structure this differently. I want to set privacy rules of data in one list against values and replationships in a second list - my data is a lot more complicated that a list of students, teachers and classes, and I have multiple tables and relationships that are not appropriate to all be bundled under the User…
Is there a plugin that can do this, or is there a timeline for this being implemented as suggested in the linked post?