Retrieve position ranking in json facets

It would be fantastic to have the position (in terms of a specific stat or count) ranking in the json facets. Let's suppose we have the field "client" of type string and we make a facet to see the top 10 (limit:10, offset:0), so the first bucket will have the ranking 1, the second bucket will have the ranking 2, and so on. Now we ask for the top 10 starting from 10 (limit:10, offset:10) so the first bucket will have the ranking 11, the second one ranking 12, and so on. Until now, there is no big deal, you just sum the offset with the bucket position.
But what happens if I want to know the ranking of a specific client (or a list of them)? One possible way would be to ask for all clients (limit:-1), but it will have performance issues on fields with big cardinality.

So, I'm asking for an option that receives a list of terms and a stat, and returns the list of terms with their respective position (or ranking) that produce the query.