If someone repeatedly abuses the system, and gets flagged enough, their rep will drop to the point that they CAN'T vote on ANYTHING. That'll teach the fuckers.
They can still vote, but their vote won't increase the REP much if any, yet their vote will be worth exactly the same amount as before. In effect you cannot stop people by flagging them, or hope they change for the better because of flagging, because they can keep self voting and someone will always have to flag them. The solution is to have a running post that goes up every week and the people that self vote rabidly can get named and people can go through their comments and flag them as a community so that the self voters will be faced with continued flagging or change their MO.
This post would be directed at everyone that bot votes from themselves as well, and I think it will be feasible as we don't have that many users with large accounts.