Apologies if I'm missing something but why can't you use a secure service provider to ratify memberships with some form of ID? I know it's seems simple but if you had to link a PayPal or credit card you could quite easily stop the dickheads from joining, unless they went to a lot more trouble. If you use a third party details would be kept secure and not in the hands of the mods. Alternatively move your service provider to Russia or China, I doubt they care about takedown requests (this is just an assumption).
Or go the other way.... Lift their bans and allow them to post, it might dissi