While the unified server approach is fantastic, there are times when it falls flat on it's face.  Consider the following (real) example.

I have access to 2 servers (news.individual.net and news-server.rr.com, call them P and S respectively)

P does a good job of filtering out most of the spam that gets injected and carries most of the groups that I want to subscribe to, leaving out the binary group I want to follow, ABPW).

S does a non-existant job of filtering spam, and carries all of the groups that I want to follow, including ABPW.

Ideally, I'd like to be able to tell pan to look for the groups ONLY on P unless I tell it otherwise.   I guess that would essentially turn it back into the old multiple server setup but would have, from the "normal use" perspective, the appearance of a unified server (ie all the groups appear in the group list regardless of which server they exist on.

I've solved the problem "for now" by editting the various newsrc-xxx files to eliminate all of the groups I don't want to get from S, however if a "refresh the group list" ever happens for S, all of that spam comes flooding back in.