The following is an Argument for the Centrality of the Eucharist in the gospel.

 The gospel is promised by the Old Testament prophets to be a -

 1) new Exodus (Isaiah 40-55),

 2) new Creation (Isaiah 65:17),

 3) restoration of Israel (Isaiah 11:11; 43:5, 6; Jer 31:8-10, et al)

 4) In-gathering of the Nations (Isaiah 11:9, 43:9 et al) to Zion (Isa 52:7-10)

 5) a new covenant (Jer 31:31-34).

 6) The kingdom of God (Dan 2:44, Zech 14:9, Hab 2:14)

 1) The Eucharistic Gospel within the Exodus Theme

 The old Exodus began with a Passover sacrifice and meal (Exodus 12), and continued in the wilderness as a journey with the manna (Exodus 16), to the promised land where Israel covenant life with God was that of a priestly son of God in union with God as his divine spouse (Isa 54:5).
So too the new Exodus begins with a new Passover sacrifice and meal (Matthew 26:26-28, Mark 14:22-24, Luke 22:19b-20), and a wilderness experience with the new manna (John 6).
As the Eucharist is both the new Passover sacrifice and the new manna in the desert, the Eucharist is essential to the gospel.

 2) The Eucharistic Gospel within the Creation Theme

 The old creation was Israel's covenant life with God, whereby Israel was the first born son (Ex 4:22), and the new Adam as head of the human race.
The new creation is therefore analogous to the old creation whereby the church as the new Israel of God and the new Adam, within the new covenant.
The old creation as Israels covenant life is centered upon the liturgical sacrifices and liturgical laws of the temple.
Analogously the new creation is then centered upon the liturgical sacrifices and liturgical laws of the new temple as Christ and the Church.
Such liturgical sacrifices Christ and the Church is fittingly enacted in the Eucharistic sacrifice as part of the new creation.

 3) The Eucharistic Gospel within the Restoration of Israel Theme

 The old Israel consisted as twelve tribes who acted in covenant union with God as a kingdom of priests (Ex 19:6). Israel was effectively destroyed through the two exiles into Assyria and then Babylon, never to return to its glory under king David and Solomon.
The restoration of Israel is promised to occur in the OT prophets along with the gathering of the nations to Zion (Isa 25:9, Ezek 37).
As the restored Israel of God, the Church is the anti-type of Davidic Israel. As such, then the church must have Yahweh as the spouse just as Israel had Yahweh as a spouse (Jer 3:1-14).
But Yahweh had Israel as a spouse through a covenant sacrifice and covenant banquet meal (2 Sam 6), as a divine marriage banquet.
Hence the church as the restored Israel must also have an analogous covenant, divine marriage banquet.
Such as banquet in the Church is the Eucharistic banquet whereby Christ is made present as both the groom of the church and the banquet.

 4) The Eucharistic Gospel within the In-gathering of the Nations Theme

 The nations are promised to be gathered to a mountain to participate in the Messianic banquet (Isaiah 25:6-9) as an act of salvation for the resurrected peoples.
6 On this mountain the Lord Almighty will prepare
a feast of rich food for all peoples,
a banquet of aged wine—
the best of meats and the finest of wines.
7 On this mountain he will destroy
the shroud that enfolds all peoples,
the sheet that covers all nations;
8 he will swallow up death forever.
The Sovereign Lord will wipe away the tears
from all faces;
he will remove his people’s disgrace
from all the earth.
The Lord has spoken.
9 In that day they will say,

 “Surely this is our God;
we trusted in him, and he saved us.
This is the Lord, we trusted in him;
let us rejoice and be glad in his salvation.”
Baptism is the sacrament of resurrection (Rom 6:1-11), whereby Christians are then brought into the sacramental economy to participate in the Eucharistic banquet in the Messianic age, just as new members of the Mosaic covenant were brought into the Passover meal after circumcision (Ex 12:43-49). The mountain of Isaiah is the new Zion as the church (Isa 25; Dan 2), where God resides as groom and host of the banquet.
The Eucharistic banquet is the banquet sacrament of the Messianic age.

 5) The Eucharistic Gospel within the new covenant Theme

 The old Mosaic covenant was confected through the sacrifice of an animal and the banquet union of Israel with Yahweh on Mt Sinai (Ex 24:11).
The new covenant is then a fulfillment of the old covenant, which will bring about a far greater sacrifice and far greater banquet between the Church as the new Israel and Christ as the groom of the Church (1 Cor 5:7-8).
The Eucharist is the sacrifice and banquet of the new covenant fulfilling the old Mosaic sacrifice and Mosaic feast on Mt Sinai.

 6) The Eucharistic Gospel within the kingdom of God Theme

 The old Israel consisted as twelve tribes who acted in covenant union with God as a kingdom of priests (Ex 19:6).
Therefore the church as the fulfillment of the old Israel is also a kingdom of priests (1 Peter 2:9).
As the old kingdom of priests performed sacrifices, then the church as the new kingdom of priests (Mal 1:11) will also performed sacrifices.
The Eucharistic is the anti-type fulfillment of the old Israel as a kingdom of Priests, whereby the Eucharist is a sacrifice confected by the church to fulfill the promises of the prophets for a universal priesthood (Isa 66:19-21) and a sacrifice performed by the gentiles (Mal 1:11).

 Conclusion - As the Eucharist is central to the above six themes within the gospel as promised by the prophets, the Eucharist is central to the gospel.

JM