Show Fieldtypes in the Realtionship - Window
In the Relationship Window is would be helpfull, if all fieldtypes are shown, not only a Keysymbol for the indexfield.
Seems like a cool idea. Just an FYI only ... note that you can Right Click over any table in the Relationship Window and immediately open the Table in Design View. Not a replacement for your idea, but just so you are aware in case you are not.