Problem: Often times, when a change is made to one page, other related ones are forgotten about, leading to inconsistencies between pages.
Proposed solution: Don't know. Ideally, there would be a pop-up box that would remind you to edit the other page, giving the relationship and what kind of data needs to be considered for the update. The pop-up should be granular, such that it could apply for either any change on the page, or changes to a specific section. Also, it would be helpful if only users who are logged in were able to set these interdependencies.
Who would benefit: Editors would get reminders, allowing them to update the other pages. Additionally, users of Wikipedia will find information across pages to be more consistent.