ummmm, your suggestion will not stop abusive posters bringing their posts back into latest postings will it? Nor will it put them off submitting new posts. So why not let the moderators remove their posts/answers? I cannot put it any more concisely than that.
the removal need only be temporary, though, same as the suspensions. Any moderators thought to be abusing the process could be stripped of their superpowers like Chuck Connors in Branded.