I just figured out a possible timeline for the authorship of the gospels.
Matthew writes his gospel "Q" in Aramaic. This resolves the mystery of "Hebrew Matthew" and universal claims that he wrote his gospel first even though Mark appears to be the source.
Mark composes his narrative gospel in a form similar to what we have today.
Marcion, an anonymous person, or Luke authors the original gospel of Luke, paraphrasing Matthew/Q and Mark plus some extra details not included in them. This gospel is issued to the gentiles.
Matthew/Q is passed around Jewish communities who add anti-gentile and pro-OT-law interpolations.
Q/Matthew is translated into Greek and merged with Mark, giving it a closer resemblance to what we have today. It may have used a bit of Luke for better consistency, explaining the minor agreements between Matthew and Luke against Mark.
The gospel of "John" and the 3 Johannine epistles are written by a Johannine community.
Virgin birth narrative added to Luke (chapters 1-2), and Matthew is updated to conform over time. This lines up with the fact that "Hebrew Matthew" was considered heretical because it apparently said Joseph begat Jesus.
Polycarp, Irenaeus, Origen, etc. begin fighting with Marcion. They become reactionary and immersed in the "us vs them" mentality. They redact the New Testament, making the last major editorial changes including interpolations and edits supporting current church doctrine, and forge new letters for the apostles (note that this was considered an act of nobility in ancient times). They especially target Luke and Marcion's favorite books for obvious reasons. The Alexandrian text type is born.
This timeline makes a lot of sense me, and would resolve quite a few mysteries about the early church and the composition of the gospels.
there doesn't seem to be anything here