Publishing could benefit from a structured way to indicate one piece’s relationship to another.
The first type of relationship could be a series. The relationship type would be managed with custom taxonomies.
When writing a post, the author would indicate the posts’ relationships to other posts in a post metabox. After publishing, an infobox would automagically appear on the public-facing view for all of the related posts.
One question is whether the relationship would be defined by the series of posts, or whether you’d want to have a separate, customizable relationship object so you could personalize the infobox.
With this type of low-overhead but valuable functionality, you’d win a whole lot of context for the first-time reader.