I ran into a video on the "Structure" plugin from ALM Works for a competing issue tracking tool. Although I don't like that tool, I like the functionality added by the plugin.
See this video: https://www.youtube.com/watch?v=WcY6zIKUMw8

Basically it allows arbitrary hierarchy structure views on the work items. There are a number of things I like:

• You can make any hierarchical structure as you like, and as many as you like.
• You can derive a hierarchical structure from existing work item relationships (e.g. links) and keep it in sync (e.g. when adding a link, the structure is adapted automatically, or when changing the hierarchy a link is adapted accordingly)
• The structure does not affect other functionality of the tool and does not require other functionality to be adapted
  

I would like similar functionality on IBM Rational Jazz solutions too. What is your opinion?