I've been working on a proposal for implementing a sub-article like functionality in the mainspace using templates. My reasoning here is simple - we often have multiple articles on very closely related topics. From an editorial perspective, these are generally treated as wholly discrete and separate items. Discussions of one article do not apply to or happen on another, etc. From a reader's perspective, the divisions are less rigid - if I am learning about Descartes on Wikipedia, every article on the topic is, for me, part of a related whole.
By finding a way to think about linked articles as a whole, we improve our ability to deal with coverage systematically.
Ergo my proposal: http://en.wikipedia.org/wiki/User:Phil_Sandifer/Branching
The biggest hurdle I see is the question of control. Like categories, branching provides a great opportunity to screw up a lot of things quickly. It violates the basic wiki principle of having things that are easy to do be equally easy to undo. Which means we probably need to develop some sort of way of controlling when articles branch. I would imagine that a white list of accepted reasons (Books by an author can always branch off of that author, episodes of a TV series can always branch off of the TV series, etc) and a Branching Proposals page where other proposals can be considered by the community would be a good idea, along with policies that make merging branched articles and deleting ill-advised branches easy.
What do people think? I'd love comments and thoughts about how to proceed implementing this.
Best, Phil Sandifer