... the author of Luke-Acts effectively buried the legacy of James, and enshrined Peter and Paul as parallel founders of the first-in-Jerusalem-finally-in-Rome Church.
That's the way I see it too (though more so Paul than Peter). That is where Acts ends after all, with Paul in Rome.
28:30-31:
For two whole years Paul stayed there in his own rented house and welcomed all who came to see him. He proclaimed the kingdom of God and taught about the Lord Jesus Christ—with all boldness and without hindrance!
Acts doesn't really identify James at all and doesn't say what happens to him, nor does it say what happens to Peter. I see it as being more about smoothing over the differences between Paul and Jewish Christians while at the same time favoring Paul.
I used to despise Acts as worthless fantasy, but lately I've come to have respect for it. I think if you factor in the above and all the ancient "special effects" (which other NT writings exhibit too, so that's just par for the course), there is some important information in Acts, even if you think it is late as I do (I reckon it's somewhere in the early to mid second century CE).
I'm not big on what "sources" various NT writings use, but Acts is an exception. For example, I think Luke/Acts knew Mark and Matthew (and not Q) and MacDonald makes me think the author knew Papias as well. And Ben wrote something in another thread regarding Papias' account of the gospel of Mark and the Mark in 1 Peter that is worth quoting in full:
Luke 1.2 says that the gospel message was passed down by "eyewitnesses and attendants of the word," the Greek word for "attendant" being ὑπηρέτης, the same word used of the person in Luke 4.20 who seems to be in charge of keeping the scrolls of the synagogue. (The word can also mean "officer," however, so this connection is not automatic.) At any rate, in Acts 13.5, Paul and Barnabas are said to have "John as their attendant," using the same word again (this John is John Mark; refer to Acts 12.12, 25; 15.37).
And think about the threefold cultural nexus at which this John Mark is supposed to work and live. His mother lives in Jerusalem (Acts 12.12) and he bears a Jewish name (John), thus giving him Hebrew/Aramaic roots; but he also helps Paul, who apparently preaches and writes in Greek; and he also bears a Roman/Latin name (Mark = Marcus). Compare this trifecta to the gospel of Mark itself, which has stories allegedly of Hebrew/Aramaic origin (translating several of the Semitic terms into Greek for the reader), is written in Greek, and also bears many Latinisms (not to mention its alleged Roman provenance), including the translation of a couple of Greek terms into Latin.
Mark's mother purportedly living in Jerusalem is interesting for another reason. The gospel of Mark, in presenting the Galilean ministry, comes off as a string of individual episodes which could be chronologically rearranged without damaging the sense of things. But the Jerusalem stuff is more of a narrative; events cannot be rearranged willy-nilly without impacting the flow of things.
Furthermore, the gospel of Mark has a lot to say about Peter; simultaneously, it seems to touch upon Pauline themes and ideas a lot, as well, and probably (it seems to me) drew from several Pauline epistles. And, of course, we find Mark being associated with Peter in 1 Peter and with Paul both in Acts and in Colossians 4.10; Philemon [1.]24.
So a purely circumstantial case can be made that this John Mark had something to do with the gospel of Mark. Yet finding firm statements to this effect from people whose access to the information can be accurately traced is a different story. Papias' transmission of John the elder's words is the closest we come.
So these days I'm thinking that the author of Luke/Acts knew some things about early Christianity (just like they say from the outset) but is spinning the information to favor Paul (and Rome) and downplay his differences with Jewish Christians.
You know in spite of all you gained, you still have to stand out in the pouring rain.