If the caller can authenticate with the services, I think you can write some rego that does something like this. I'm interested in what the flow looks like. Does the caller talk to A first to initiate this delegation?
if you use something like OPA, it has partial evaluation [1], which would allow you to read in data, filter it based on your RBAC policy quickly until you have a pageful, then return to the caller together with some next page token that lets you remember where you left off.
I think you need multiple generations (subsequent) of stars in order to get heavier elements - which are probably needed by life.
So maybe the universe is not _that_ old.
Reminds me of Feynman's anecdote about how math textbooks were evaluated by the Curriculum Commission.
"The reason was that the books were so lousy. They were false. They were hurried. They would try to be rigorous, but they would use examples (like automobiles in the street for "sets") which were almost OK, but in which there were always some subtleties. The definitions weren't accurate. Everything was a little bit ambiguous – they weren't smart enough to understand what was meant by "rigor." They were faking it. They were teaching something they didn't understand, and which was, in fact, useless, at that time, for the child."