My present favourite thought on how to accomplish this is by processing the published post's links (including both the optional Link: field and any <a href> tags in the post body), to sum up a list of outbound links. Then, for each link in that list, fetch the pointed to page, processing it for structured announcement of a trackback URI for that page (via the RDF markup standardized for this purpose -- there may be hairs to split about how to behave, in case a page would specify more than one trackback URI -- I'll leave that for further pondering and discussion). Filter out all the URLs from the list which did not yield one trackback URI. For each of the links left, add a "Trackback ping" link on the "post published" page.
Points for style awarded for stylishly formatting this list, relating it to A) the linked URL, B) the <a href>link contents</a>, C) the trackback ping of the resource. I'd appreciate any suggestions and HTML mockups very much; this is a bit of my weak spot.
Additional points of style for an additional list, clearly separated from the first, for the filtered out links (and marked as such) for the links lacking a trackback URI we could find, for human manual visit, to pick up any such trackback URIs (as I'm sure many are only marked up for human visitors to find), and related machinery to add the trackback URIs to these, and have ping functionality for them as well. (The mechanics part of which I will also manage myself without any problems.) Aid on the visiofunctional design, again, much appreciated.