Nice try, except those who open the Bible believing every "i" and "t" in it is the pristine "word of God" will also believe the "according to Mark" means that it was truly Mark (for God doesn't lie!), the follower of Peter, who wrote it.
Calling it the "First" or "A" Gospel would not lead to such erroneous belief. Those Gospel titles are misleading and most Christians have never heard that Gospels are anonymous writings.
“most Christians have never heard that Gospels are anonymous writings”
Do you actually KNOW most Christians? I thought not. Most people don’t particularly care, but if they do, any study Bible or commentary will give them ample background information. But I’m sorry to hear the Christians you’ve met don’t study much...
“For and against what?”
For and against theories about who wrote them. Overall, I’d say the majority of conservative Protestants would have Matthew, Mark, Luke and John as the writers, based on reasonable evidence. I do not know of any who would be upset if they found out otherwise, but I don’t tend to travel in KJV-only circles.
“What external evidence?”
Generally tradition, with tradition sometimes including multiple possibilities.
“The Hebrews would have not been accepted had they not been assumed to be Pauline.”
Some still say it is. Others say Barnabas, who was a close associate of Paul’s. Luke was accepted, and Mark, without requiring direct Apostolic authorship.
But if you don’t wish to accept Hebrews, I cannot stop you. I do. Martin Luther agreed with you, but not quite strongly enough to actually remove it from the New Testament.
“No, they just quietly removed them form subsequent editions while still maintaining that God made sure not an iota has been corrupted, because once you do the unraveling of the Bible myth becomes unstoppable.”
Maybe because removing them didn’t affect doctrine? The Trinity wasn’t based on those, was it? We’ve argued the trustworthiness of the text before...you believe the authorities you trust, and I believe the authorities I trust.
“And what would all the Bible thumpers do for a living if they couldn’t peddle the Bible as the word of God? Flip hamburgers?”
I’ve known Baptists who flipped hamburgers. Good guys, too! I’ve thumped a Bible or two, and I’m a retired Electronic Warfare Officer. We Bible-thumpers tend to trust God to get us through - but I wouldn’t put the Osteens in as Bible thumpers. From what I’ve seen, they pay no attention to the Bible at all.