Specific unequivocal Scriptural evidence that important J W doctrines were clearly Christian teachings, and did not rely on the interpretation of men : e g , medical use of blood, Celebrating holidays, the addition of Jehovah's name in the New Testament, the mass slaughter of non WT believers at Armageddon etc.
Confirmation that The Watchtower Society really had lived up to its high ideals and not allied itself secretly to the United Nations, and that every time a secular authority is quoted in the lit, it is quoted honestly and fairly. That whenever the WT discusses its past, it does so honestly and fairly.
That would make me take notice ...