The problem from the Latin/Greek Chalcedonian view, with Subdeacon Peter's statement is "one hypostasis". What he describes is actually miaphysitism, Christ has one nature that is perfectly human and perfectly divine.
The trouble is that this IS the teaching of St Cyril. I didn't invent 'one incarnate hypostasis of the Word'.
Of course I don't believe that Christ is 50% human and 50% divine. He is perfectly and completely both. But are you saying that Christ has two hypostases? That is, he is two individuals? This is what the Nestorian Church of the East still teaches.
Surely the 5th council also says that Christ is one hypostasis:
"If anyone understands the expression "one only hypostasis of our Lord Jesus Christ" in this sense, that it is the union of many hypostases, and if he attempts thus to introduce into the mystery of Christ two hypostases, or two Persons, and, after having intro- duced two persons, speaks of one Person only out of dignity, honour or worship, as both Theodorus and Nestorius insanely have written; if anyone shall calumniate the holy Council of Chalcedon, pretending that it made use of this expression [one hypostasis] in this impious sense, and if he will not recognize rather that the Word of God is united with the flesh hypostatically, and that therefore there is but one hypostasis or one only Person, and that the holy Council of Chalcedon has professed in this sense the one Person of our Lord Jesus Christ: let him be anathema. For since one of the Holy Trinity has been made man, viz.: God the Word, the Holy Trinity has not been increased by the addition of another person or hypostasis."
If I may briefly quote a few other Chalcedonian sources:
"in Christ there are two natures and one hypostasis"
Fr John Romanides says:
"To speak about two natures in Christ [for a non-Chalcedonian] would be somewhat equivalent to a Chalcedonian speaking about two Hypostases in Christ. In this respect 'a Chalcedonian would accept and does accept everything Cyril says but would use Cyril's One Hypostasis of God the Logos Incarnate, since for him Physis means Ousia."
Fr Luke Holden - Greek O priest
"In a period when it was becoming common to speak of Christ as one because His human and divine natures are the natures of the one hypostasis of the person, Nestorius spoke of a union kat’ eudokian, a union in will. "
"The Catholic Church defended Christ: One person, one hypostasis, two natures."
Statement of the 6th Council
"believing our Lord Jesus Christ, our true God, to be one of the holy Trinity even after the taking of flesh, we declare that his two natures shine forth in his one hypostasis, in which he displayed both the wonders and the sufferings through the whole course of his dispensation, not in phantasm but truly, the difference of nature being recognized in the same one hypostasis by the fact that each nature wills and works what is proper to it, in communion with the other. "
I'll stop there. I'm just trying to suggest that what you posit as a point of possible misunderstanding, which I can accept, nevertheless is entirely in accord with EO and RC documents. Since the latter councils all speak of 'one hypostasis' I think I might ask why you (and any others) have a problem with the phrase.
If I cannot confess my faith in Christ using the language of the latter EO councils then how can I at all?