OK, now I’ll argue from reasoning, though my “passion” for a truly “organic” celebration (as set forth in Sacrosanctum Concilium) of the Eucharist and the liturgy is the primary basis for my critique.
Yes, the Mass is a sacrifice, though the new “Lamb of God”-only mandate focuses exclusively on the Passover (Paschal) interpretation of the Eucharist. Biblically, that shows up as the “new covenant” language in 1 Corinthians 11:25, Mark 14:24, Matthew 26:26-28, and Luke 22:19-20. Yet John 6:31-35, which we just heard in the Sunday readings of the Gospel a few weeks back, emphasizes the Exodus linkages of the Eucharist. So to say that the Eucharist is exclusively Paschal is to constrain our interpretation of Christ’s giving of his body and blood more narrowly than the range we have in scripture. The Johannine Eucharistic language (“bread of life,” “living bread,” ") is distinct from the Pauline and Synoptic language.
As a trope, “Prince of Peace” might be outside the Biblical basis of the Eucharist (though I might generously suggest that its use in Isaiah 9:6 as the foretelling of Christ might also be relevant as it is Christ’s sacrifice that is the center of the Eucharist). Others such as “light of peace” or “word of God” might also be outside the Biblical basis for the Eucharist. However, the notion that we need to keep Christological concepts outside the Agnus Dei is odd to me. Personally, I find “light of peace” a little too far removed from the sacrifice theme, however. “Word of God” is not just a reference to scripture but to Christ himself (in the Johannine tradition). That was suggested in the second reading from this Sunday (from Hebrews), and its use in the Agnus Dei would have been a nice follow-up to the reading that the Word of God is sharper than a sword, penetrating between soul and spirit, bone and marrow. Now if THAT didn’t set hearts on fire for the Eucharist…
In summary, the notion that we should focus exclusively on the Paschal nature of the Eucharist, when the Johannine Biblical texts do not themselves mention it, is to take a reductionist (or fundamentalist) view of the Eucharist that doesn’t square with the diversity of Biblical texts. The Johannine langugage simply doesn’t tell us to focus on the Paschal nature of the Eucharist, unlike the Synoptic and Pauline Eucharistic verses.
So the way I see it, we now have a mandate that causes us to omit from the Agnus Dei at least one legitimate and Biblically-based way of describing the Eucharist.