Okay, I've posted a bug about this at http://bugzilla.wikimedia.org/show_bug.cgi?id=11270, with a patch implementing Brion's basic idea a little more robustly. I view it as nearly ready for deployment, after more extensive browser testing and a few bug fixes. If someone could install it on their public wiki for comment (maybe test-wiki?), that would be great.
For those who are newcomers to the discussion, this is a somewhat more refined variant on http://test.leuksman.com/view/Venus_Williams#2003, which seems to be largely broken, but a screenshot is available at http://i17.tinypic.com/68jnvo4.jpg. For "why do we want this" and other general discussion, see the history of this thread beginning at http://lists.wikimedia.org/pipermail/wikitech-l/2007-June/031899.html.