How about Mailwasher automatically searching for an unsubscribe link in Spam messages. If found then automatically activate the link.

Really bad idea, most spammers use the unsubscribe link to collect information about you and your account. By clicking it you confirm they have a live address that looks at spam along with information about your system and connection.

Best to just report your spam to spamcop.net using the MW tool, that will get you off any legitimate list and quite a few spammers too.