I do not see the point in this letter, and the writer is trying to be too clever for their own good.
If a person does not want to disassociate, it is best not to do anything, just fade. By stating you do not agree with certain teachings of the Governing Body, you then admit to being what Watchtower regards as apostate and liable to be disfellowshipped.
Whilst one of the criteria to avoid being disfellowshipped is not recognising the authority of the elders and Watchtower, another is whether you are considered as one of Jehovah's Witnesses by the congregation and community, and hence they can still disfellowship you on that ground.
The elders will not provide names of accusers, or put things in writing, particularly to someone that just said they don't recognise their authority. Nor will they be frightened off from announcing a the person is no longer one of JWs, since it has been almost impossible to win a case when sue an elder for such a statement.
If the person genuinely does not want to be harassed by the elders, then write a letter saying that any calls and visits are causing distress and that an AVO will be sought. But the tone of this letter does not make it sound like harassment is the cause behind why it was written.