Conceptually, the project wouldn't be very difficult to implement in that we have a lot of things going for us. Proxy servers are maturing, cache servers are maturing, HTTP and NNTP are stable protocols. There is plenty of sample code available that works almost like what we'd need. Would also send out locally posted news to legacy servers, as well as using some form of IPC to feed incoming header info to the overview daemon. Would also send out to other overview daemons locally posted overview data.
NNTP clients stay the same, for now.
Eventually, they will be able to talk directly with the cache server. I should note here that direct-spool readers are going to get shafted with any of the proposed spool changes and that it is not unique to this proposal. Well, HTTP provides every mechanism you need to do news transfers. In fact, it will take months for a useful-sized network to start using any new technology. When articles come in to the article daemon, it would generate overview data stating that the local cache is the most authoritative place to get the news article.