• The Laws of Logic Hold Universally
• Christianity's distinctive, characteristic beliefs

• the Son is subordinate to the Father
• if the Son is subordinate to the Father, then the Son is not fully God
• If the above is true, x the Son has always been fully God

∴ x the Son has always been fully God

Arius (cf. Arianism)

• the Son is less divine than the Father
• if the Son is less divine than the Father, then the Son is not fully God
• If the above is true, x the Son has always been fully God

∴ x the Son has always been fully God

Arius (cf. Arianism)

• Jesus was a human that God adopted to be Messiah (cf. Adoptionism)
• If Jesus was a human that was adopted to be Messiah, then the Son is not fully God
• If the above is true, x the Son has always been fully God

∴ x the Son has always been fully God

Arius (cf. Arianism)

• Jesus was a mere man
• a mere man cannot be God
• If the above is true, x the Son has always been fully God

∴ x the Son has always been fully God

Ebionites

• God is simple
• the Father is God
• the Father is unbegotten
• Jesus is begotten
• x God being both unbegotten and begotten accords with God's simplicity
• If the above is true, x the Son has always been fully God

∴ x the Son has always been fully God

Opponents of Gregory of Nazianzus, Theological Orations #3, https://www.newadvent.org/fathers/310229.htm.

the Son has always been fully God

It seems there's two lines of reasoning here: those that disagree with the Son being fully God and those disagreeing that the Son has always been that way. Perhaps all the reasoning that affirm “x Jesus is God” should be moved under that statement, and then “x Jesus is God” could become a line of reasoning here.