sorry I missed this message.
At the moment we don't offer this functionality, but we have RankProfiles, where you can request the rank of up to 1000 pubkeys in a single call.
https://vertexlab.io/docs/services/rank-profiles/
A similar idea would be to return a bitset containing all pubkeys whose rank is higher than a threshold according to an observer/source (for example using sort=personalizedPagerank and source=your npub).
What is the usecase that u have in mind?