Such integration is very useful, for example to drag&drop a class to a diagram or ctrl+click on a diagram to navigate to the code.

The plugin should support at least the following

• class & sequence diagrams
• export as image
• reverse engineering (this way it can be used to explore existing code written by others)
• navigation from a diagram element (package / class / field / method) to the thing it represents
• ability to drag & drop classes on a class diagrams and the plugin will automatically add relationships arrows (implements / extends)