Cross-reference requirements/specifications/implementations?
Low-priority, but it would be great if we could cross-reference requirements (like "The processing may be limited to a maximum total number of records, processing the "first" X items and exiting.") to the specifications of interfaces fulfilling that requirements, and from the specifications to the implementations of the functionality. And/or the reverse direction (why is this in the interface? Here's the specification, and the requirement...).