The method in the IRenderer interface wouldn't help, because it refers to the visibility list, not to a single object. With the default pipeline, wireframe per object just isn't possible in a reasonable way at render time. With the compiled pipeline in the 1.18 beta, it should be possible somehow if the object has been compiled.
Something that will work for both (but is a bit ugly), is to render the World twice. Once in normal mode with all objects visible. Then, iterate through all world objects, store their visibility, set them to invisible except for the ones that you want to render in wireframe, render the world again and draw it in wireframe, reset all world objects to the correct visibility. It's ugly, but once wrapped into a small method that will take care of these steps, it should be pretty easy to use...it won't be very fast, but it should be sufficient for debugging purposes.