Persistant spammers would have to be dealt with on a time-by-time basis, as they are now. A combinatin of general-IP banning as well as requiring users to validate through email (spammers are unlikely to create a new email address just to return and be banned again), has been quite effective for me.
I'm not so bad at coding myself, so I could try and help out anyone who would be willing to construct this hack, if it would be needed.. but I'm nowhere near as good as most on here that would be needed to make this hack.
Anybody willing?