Filtering what is available for federation

Hi guys,
I have a use case that seems a bit unusual for federation.
In my use case, all data center metrics are scraped by a prometheus instance let’s call it “Paul”. I am managing that prometheus instance.
I would like to make available to “John” (another prometheus instance managed by another team) a subset of metrics.
My understanding of federation is that the “filtering” is made on John’s side through match
So, John decides what is wants to scrape based on the “match”.
Paul has no control on what can be scraped or not.
In fact, I would like to decide on Paul’s side which metrics can be scrape by John.
So, some kind of filtering on metrics that can be scraped. Is that doable?
At the moment, my option is to create a Paul2 with the appropriate match so that John will scrape Paul2 where only a subset of metrics (defined by me) are available. It creates another prometheus instance. No big deal, but, not elegant either.
Any better ways of doing what I’d like to do?