Irenaeus was not in fact developing his arguments from a Marcionite gospel or a Marcionite Apostolikon. Instead he was arguing from Luke that the Marcionite gospel was a corruption of that text. Yet he did not even have a copy of the Marcionite New Testament to make his study reliable. We can in fact demonstrate that he used a lost original treatise - likely written by either Justin or Theophilus - which made a very different case, one that had nothing to do with alleged Marcionite corruptions to the gospel of Luke. Irenaeus's source developed an argument that the Marcionite's shorter gospel unnecessarily abridged a gospel harmony (or 'Diatessaron'). The source likely did not even view this original gospel as a 'harmony' but in fact the proper length and constitution of the narrative.
What makes this so interesting I think is that we arrive at a situation where Clement's two gospel of Mark - one long and one short - perfectly fit the context of the original Marcionite debate. Lesser Mark (= Gk. Marcion) was controversial because it was argued that the full gospel should not be shortened. This is clearly where Irenaeus's argument that the heretic 'cut' things from the true gospel. Irenaeus's cleverness however was to adapt these original arguments - which were in a sense 'true' and reflective of a historical reality - towards a historical claim that was a lie i.e. that the Marcionites possessed a 'cut' gospel of Luke.
I do not have time to go into greater detail with respect to those specific questions right now. Instead I would just like to continue our moving away from the traditional understanding of the Marcionite canon - i.e. that it simply represents the same gospel and epistles from our own canon only 'cut' to something which would appear 'centonized' to the naive observer - especially those who only knew the shape and the order of the individual Catholic gospels and epistles.
We already demonstrated - I think successfully - that the Marcionite gospel imitates the Diatessaron insofar as the 'blessed is the womb' statement immediately precedes the question about Jesus's mother and brothers - cf. Against Marcion 3:11 "For a certain woman had exclaimed, Blessed is the womb that bare You, and the paps which You have sucked! (Luke 11:27) And how else could they have said that His mother and His brethren were standing without? (Luke 8:20) The question for us now is whether there are other examples which furthermore can be used to tie the Marcionite canon to that of Clement of Alexandria.
Here are some citation parallels worth considering including Philippians 2:6 coupled with Colossians 1:15:
For he says of Christ, that, being in the form of God, He thought it not robbery to be equal with God; but emptied Himself, and took upon Him the form of a servant, not the reality, and was made in the likeness of man, not a man, and was found in fashion as a man, (Philippians 2:6-7) not in his substance, that is to say, his flesh; just as if to a substance there did not accrue both form and likeness and fashion. It is well for us that in another passage calls Christ the image of the invisible God. (Colossians 1:15) For will it not follow with equal force from that passage, that Christ is not truly God, because the apostle places Him in the image of God, if, as Marcion contends, He is not truly man because of His having taken on Him the form or image of a man? (Against Marcion 5.20)
And the Word was God also, who being in the image of God (Colossians 1:15), thought it not robbery to be equal to God. (Philippians 2:6) Thus, that clay which was even then putting on the image of Christ, who was to come in the flesh, was not only the work, but also the pledge and surety, of God. (Resurrection of the Flesh 6)
The problem with this parallel is that Philippians mentions 'the form of God' which might have been rendered as 'image of God' in the Latin text or it might have been a natural parallel exploited by more than one author.
This next one between Clement of Alexandria and the Syriac Testament of the Lord is far more convincing:
But the saints of the Lord shall inherit the glory of God, and his power. Tell me what glory, O blessed one. That which eye hath not seen nor ear heard, neither hath it come upon the heart of man; and they shall rejoice at the kingdom of their Lord for ever. Amen. (Clement Exhortation 10)
And the righteous, that have walked in the way of righteousness, shall inherit the glory of God; and the power shall be given to them which no eye hath seen and no ear heard; and they shall rejoice in my kingdom. (Syriac Testament of the Lord).
The point is that we have to go through all 'coupling' of lines from apparently separate Pauline epistles and see if they appear more than once including:
But since You lead me to the light, O Lord, and I find God through You, and receive the Father from You, I become Your fellow-heir, Romans 8:17 since You were not ashamed of me as Your brother. Hebrews 2.11 (Exhortation to the Heathens 11)
For although the Scripture says, Shall the clay say to the potter? Romans 9:20 that is, Shall man contend with God? Although the apostle speaks of earthen vessels 2 Corinthians 6:7 he refers to man, who was originally clay. And the vessel is the flesh, because this was made of clay by the breath of the divine afflatus; and it was afterwards clothed with the coats of skins, that is, with the cutaneous covering which was placed over it. So truly is this the fact, that if you withdraw the skin, you lay bare the flesh. Thus, that which becomes a spoil when stripped off, was a vestment as long as it remained laid over. Hence the apostle, when he call circumcision a putting off (or spoliation) of the flesh, Colossians 2:11 affirmed the skin to be a coat or tunic. (Resurrection 7)
Even the apostle ought not to be known for any one statement in which he is wont to reproach the flesh. For although he says that in his flesh dwells no good thing; Romans 8:18 although he affirms that they who are in the flesh cannot please God, Romans 8:8 because the flesh lusts against the Spirit ... However, let me meanwhile add that in the same passage Paul carries about in his body the marks of the Lord Jesus; Galatians 6:17 he also forbids our body to be profaned, as being the temple of God; 1 Corinthians 3:16 he makes our bodies the members of Christ; 1 Corinthians 6:15 and he exhorts us to exalt and glorify God in our body. (ibid)
For although it is called a vessel by the apostle, such as he enjoins to be treated with honour, 1 Thessalonians 4:4 it is yet designated by the same apostle as the outward man, 2 Corinthians 4:16 — that clay, of course, which at the first was inscribed with the title of a man, not of a cup or a sword, or any paltry vessel. (ibid 16)
We have the apostle in another passage defining but one baptism. Ephesians 4:5 To be baptized for the dead therefore means, in fact, to be baptized for the body; for, as we have shown, it is the body which becomes dead. What, then, shall they do who are baptized for the body, Ephesians 4:5 if the body rises not again? We stand, then, on firm ground (when we say) that the next question which the apostle has discussed equally relates to the body. But some man will say, 'How are the dead raised up? With what body do they come?' 1 Corinthians 15:35 (Against Marcion 5)
