"All they announce at the meeting now is, "Brother So-and-So is no longer one of JW's." They don't actually mention anything about your moral character or anything like that, and they don't specifically say to cut off all communication with that person. The only way I can see around this would be to prove from their own literature that they command the R&F to cease talking with anyone who used to be a witness but no longer is. Any thoughts on how to incorporate that into the letter? I figure they could use the excuse that they are only announcing the termination of your membership, and nothing about your moral character. Thoughts?"
It's a tricky situation considering the Watchtower Society's habit of using language with hidden meanings. One idea is to further emphasise that you aren't resigning, you're just responding to the decision of the Watchtower Society to view you differently and no longer officially count you as a member. Theoretically, they can't later decide to take any action or make any announcements that would result in punishment for someone who is no longer a member.
It's not really a resignation letter, it just deals with removing a person's name from the Society's records which would make future disciplinary action much less likely. Laws vary by country, but I believe some countries are pretty strict about privacy rights and would possibly prevent the Watchtower Society from imposing sanctions against those who would exercise those rights.