I'm coming from an SVN (Subclipse) background. When comparing two local files or two remote revisions, Eclipse provides a "swap to and from" button but this button is not available as a preference configuration or when comparing against a remote file. When using the right click context menu, Compare with..., Eclipse will always position the local copy on the left pane and remote copy on right pane. This is not intuitive compared with all the other diff tools (including tortoiseDiff). Unfortunately Eclipse refuses to add this configuration so I'm hoping your plugin can pull it off.
A preference option under External Tools allowing Remote copy to be on Left or Right pane would be great!