I do believe the Watchtower interpretation is untenable for a number of reasons. For those that are interested I will try to explain. The arguments for and against are clearly set out in the footnote of the NET Bible, basically the difference between the Catholic and Protestant position. Obviously the editors of NET take the Protestant position, seeing that it is a Protestant Bible:
John 6:53 (NET footnote) says: Unless you eat the flesh of the Son of Man and drink his blood. These words are at the heart of the discourse on the Bread of Life, and have created great misunderstanding among interpreters. Anyone who is inclined toward a sacramental viewpoint will almost certainly want to take these words as a reference to the sacrament of the Lord’s Supper, or the Eucharist, because of the reference to ‘eating his flesh’ and ‘drinking his blood’ (John 6:53ff.; cf. Matt. 26:26-28). But this does not automatically follow: By anyone’s definition there must be a symbolic element to the eating which Jesus speaks of in the discourse, and once this is admitted, it is better to understand it here, as in the previous references in the passage, to a personal receiving of (or appropriation of) Christ and his work. Notice that in John 6:54 (NET footnote) the result (has eternal life and I will raise him up at the last day) is produced by eating (Jesus’) flesh and drinking his blood. Compare John 6:40 where the same result is produced by “looking on the Son and believing in him.” This suggests that the phrase here (eats my flesh and drinks my blood) is to be understood by the phrase in John 6:40 (looks on the Son and believes in him).
However, I personally believe that it is no coincidence that Jesus uses this very same terminology when instituting the memorial of his death. Early on in his ministry (already in John 6) he would be preparing the people for the Eucharist. Note the context, he is speaking to all the people, including Pharisees. He also refers to Judas who would betray him (6:71).
His intimate followers, later to be anointed with holy spirit, are in a special covenant relationship with him (Matt. 19:28; Luke 22:28-30; cf. Rev. 5:9, 10). They would be celebrating the memorial in remembrance of their Lord, for forgiveness of sins as well as being participants of the new covenant as leaders of the Israel of God (Matt. 26:28; 1 Cor. 11:25; Gal. 6:15, 16; Rev. 14:1-5; 20:4). Jesus’ earthly subjects would celebrate the memorial in remembrance of their Lord, for forgiveness sins and being participants of the new covenant as part of the Israel of God. By so doing both groups would be unified in “proclaiming the death of the Lord until he arrives” and attaining the forgiveness of sins (Matt. 26:28; 1 Cor. 11:24-26; Gal. 6:15, 16; cf. John 6:56).
After the death and resurrection of the Christ, God would choose a people, made up of individuals from the nations, for his Name. By divine providence these would be called Christians (Acts 11:26; 15:14-18). However, the prophet Isaiah predicts the miraculous birth of a nation as a new creation, suddenly, and without birth pains (Is. 54:6-8, 13; 62:4, 5; 66:6-10; 2 Cor. 5:17; Gal. 4:24-27). This new nation, known as “the Israel of God” as well as the “the tribes of the people of Israel” will be chosen from the nations to replace “fleshly Israel” (cf. Is. 66:8; Dan. 9:27a; Matt. 19:28; 1 Cor. 10:18; Gal. 6:16; Rev. 7:4 NET). God will be concluding with them a new or better covenant (Heb. 8:6, 9, 10; 10:16).
Definition of a new creation is a person who is in union with Christ: “Consequently if anyone is in union with Christ [united with the Messiah, CJB], he is a new creation; the old things passed away, look! new things have come into existence” (2 Cor. 5:17). The Israel of God also qualifies as a new creation as it is born miraculously, without birth pains: “Neither circumcision nor uncircumcision means anything; what counts is a new creation. Peace and mercy to all who follow this rule, even to the Israel of God” (Is. 66:7; Gal. 4:24-27; 6:15, 16 NIV1984).
The transition
between aforementioned chapters of Revelation (6:15-17; 7:1) is introduced by
the Greek phrase Καὶ μετὰ τοῦτο (Rev. 7:1 Tischendorf’s New Testament, 8th
edition), “and after this,” “this” referring to the kings of the earth and
their followers, finding refuge in their underground shelters. If that is the
case, the sealing of the 144000 should be viewed as a future event. Note also that they
are taken from the twelve tribes of Israel (7:4).