You made a statement that 99% of Luke was anti-Marcionite, making it impossible that Luke was built on the Marcionite gospel, and that they must have developed in parallel. Setting aside that that is hyperbole, as Christians ranging from Gnostic to Ebionite agreed on most specific elements, I will give you a demonstration of a unmistakably clear Marcionite element left in Luke's gospel, one the author of Luke never would have written had it not been in the gospel he used as his base document.
The irony is I will show how the same element the Marcionite author put in to "correct" his source in one place is given away because he failed to remove or sufficiently modify the account in another place, which reveals what he did. (Honestly I think he did not realize the theological connection, so let it pass.)
I wrote a blog entry on this very subject a little over two years ago, inspired to reevaluate it as part of a critique of Markus Vinzent's model of the Synoptic gospels. But also to look at one of the very few claims By Tertullian (AM 4.38.1-2) of material being expunged by the Marcionites which I thought had some legitimate merit. You can read my evaluation of the Baptismal scene and the mechanics of how it went missing:
https://sgwau2cbeginnings.blogspot.com/ ... hn-in.html
The key points are these:
1) the Marcionites agreed with the position of the proto-orthodox that John was the last prophet of the Jews
-- all the Synoptics felt this was important, that Jesus' authority was vouchsafed by John's Baptism (e.g., the Authority of John story)
-- Matthew explicitly states that John is Elijah redivivus, the others imply it with reference to the Malachi prophecies
-- only the gospel of John rejects this
2) the Marcionites held that the Creator (who was the Jewish God) did not recognize Christ, and neither did John
-- so it holds that John would not be able to recognize Jesus (see DA 1.26 comments by Marcus the Marcionite champion)
-- the passages in Luke 7:11-28 are from the Marcionites, meant to debunk John's authority, show his inferiority to Jesus, and his ignorance of him.
3) It would have been impossible for the Marcionites to accept that Jesus could submit to John for Baptism
-- this is why the Marcionite author removed the baptism scene
-- instead he chose to begin the gospel with the start of Jesus' mission, appearing in Capernaum
-- later Marcionite exegetes would interpret the words "he descended into Capernaum" (which was probably more a phrase of the sort where we say we "went down South" in the US) to mean that Jesus descended from heaven. Scholasticism was used by all early Christian sects to explain away inconsistencies or to read into the text positions that match your views without need to change the writing. This is an important point to keep in mind when considering why texts with positions inconsistent with the theology of the sect that used them, including the Catholics, were not always adjusted, but left standing. The principle, if it can be explained way, or made to sort of fit, why bother doing work on it?
The reason we know the Marcionite author removed the appearance of John and the Baptism scene (his prototype gospel text likely very similar to Mark 1:2, 4-11) is because of the references to the passage and words drawn from it in the refutation of John in Luke 7:24-28. References to John's garments, but instead of being beggarly they are fine, and instead of living simply he is said to live luxuriously in palaces. His staff is said to be a weak reed, flimsy and so of no power. He also makes reference to the Malachi 3:1 prophecy, agreeing with the Synoptic position of John as the last prophet, Elijah reborn, and the greatest prophet. But he says he is the least in heaven, the lowest of Christians, is greater than John (implies IMO that John is not in heaven, or at least not the heaven of Christ). This is also the sentiment of those who follow Moses but not Christ in Luke 16:19-31 (Marcionite version varies slightly in the last two versus, as Luke sought to soften the opinion expressed slightly, not denigrate Moses). The lower status of John, Moses and thus the Jewish God is established, all without tossing Abraham ("father of us all").
Note: if you look at Matthew's version of the Marcionite anti-John material (verses 11:7-11), you can see he mitigates it. Unlike Luke 16:16 where the Law ends (another example of a Marcionite view left in Luke by the redactor), it is merely prophecy (of Christ to come) which ends in Matthew 11:13, the verse immediately preceding where Matthew has Jesus explicitly identify John as Elijah. Matthew further rejects the Marcionite position by stating explicitly in 5:17 that the Law is not abolished by Jesus, but fulfilled (e.g., the prophecies)
The irony is that like the Lukan redactor, the Marcionite author let material in that refers specifically to Jesus' authority being derived from John's baptism found in Luke 20:1-8. He failed to see the connection of the two authorities, and how the synoptic prototype author drew Jesus' authority from John's baptism. He merely saw this as a put down of the Jewish high priests and scribes. The scene only has importance if it is referring to the Jesus' baptism as being vouchsafed by the prophet of the OT God.
So there you have it, two elements (Like 7:11-28, Luke 16:16) in Luke that are fully Marcionite.