Some of those problems in that vein that appeared insurmountable ten years ago might have solutions in current "peer-to-peer" networking technologies (thus the off-hand comment about Napster).
What you're really asking for is a NNTP-over-FastTrack (Kazaa/Morpheus) feed object. This is sort of/really an odd idea, but if you think about it, all the required parts are pretty easy to articulate in skeleton form:
I honestly have no idea what I'm asking for when you start substituting names of real things that could be used to implement this. I recognize "NNTP," though. :-) It sounds like you're on the right track; is there a way to keep the existing distribution system for posting to per-site configurable groups from sites that fit some per-site configurable profile of article properties (fewer than X per day, size less than X, etc.)? Stephen