I have an idea: since the spambot's goal is to add links to a website, why not give admins the ability to (temporarily) filter all edits which involve a certain domain (more generally, a regex). This would apply site-wide. That is, you could prevent any edit which adds "*.spammersdomain.com/*" to a page. The code would have to be slightly clever to detect url encodings, etc., but surely doable.
Arvind