Hi again,
From what I can tell the type of gradient you are talking about isn't available in most vector graphics editors, although I agree that it would be a nice option to have. One exception I know of is Macromedia Fireworks MX which refers to it as a "contour gradient".
Canvas by http://www.deneba.com/ has some cool gradients, too.
However, if this isn't part of the SVG spec is seems like it would probably be difficult to add this type of gradient to Inkscape.
An alternative would be to add gradients via bitmap editing. The only drawback is that it is not possible to access single objects anymore. A workaround could be to export as .ai, to convert the file to .psd (Photoshop), and then to re-import it into the Gimp. I haven't tried this yet, though, still working with v 0.39.
Cheers,
Claus