Thanks GFG, I was confused, not about the original idea, as outlined again in your Posts above, but confused about if someone wanted to use the Letter to make sure, if they were merely in fact secretly disassociating, to make sure no Announcement to that effect was made at any point in the future, so that they were fully free to associate with family and friends who were JW's, could the Letter be used, in conjunction with the Law, to achieve this ?
I think probably not, if the JW's wish to Announce it, then that is what will happen, no Law could easily be used to stop that.
But I think what I missed mainly, and you have made plainer, is that if The Letter is done, and nobody else, apart from the trusted person assigned to care for it, knows about it, then in reality you ARE free ! That is a wonderful feeling for your mental health, and feeling of self worth.
In my situation, not DA'd, there is always that feeling of having to "look over your shoulder" , careful what you say and do in the sight or hearing of J.W's. Once the letter is done, stuff 'em ! do and say what you like !
It may still work out that if you are threatened with DAing, then production of The Letter may stop them doing anything further, they may well think "What's the point?", but it depends upon circumstances, particularly what provoked in the "loving" Elders the desire to take action against you.
Another thought, if at some time a family member or members decided, without the Elders being involved, to have no association with you, if you showed them The Letter, what Scriptural reason (real one, not just interpretation) could they use for such action ? "Quit mixing with a Brother that..." or whatever it says won't work, you are not a spiritual brother or sister, not a Jehovah's Witness, such unilateral action by them would have little Scriptural basis in reality.