I always seem to get the same message from the anti-scripture postings:
We did the research to determine which was legitimate, apostolic scriptures, so therefore, we get to supercede them.
That's a bit like a physicist saying, "We did the research to spell out the law of gravity, so therefore, we get to ignore it."
You've done a great job covering this ground, with the historical development of the Canon. I think the one element that gets forgotten is that Rome did not officially recognize the Canon until after the fact. Thus, the "editor's argument" would not even apply if it were applicable.