adding fuctionality to the outliner in blender 2.5

Is there a way to modify the UI of the outliner?

I am writing an exporter where the user must define the way each node of the scenegraph ist to be exported. The user can toggle between several modes for each node that is displayed in the outliner.
The ideal soultion would be to add an extra column to the outline that dispays the icon of the current mode. The user can then click on that icon to toggle between the modes. Just like the use can toggle between visible and invisible by clicking on the eye icon.