A subscription model is clearly not inconsistent with moderation -- people who pay to join clubs are still obliged to follow a code of conduct -- but I'd say it's inconsistent with the way moderation works on the site currently. At the very least, it would probably need to be easier to appeal any decision, or you could add a method of private communication with users, equivalent to taking them to one side and explaining what they have (allegedly) done wrong.
Actually, either (or both) of those changes should perhaps be considered anyway, whether or not AB switches to subscription/voluntary contributions. "Answer removed"/"thread closed" is such a catch-all that covers all manner of sins, from the minor case of being a duplicate thread on a topic to the major case of utterly inappropriate content that needs to be zapped pronto.