The last book to be added to the Christian canon was the Song of Solomon, in the 3-4th century AD. What if they had continued adding to the canon? So by the 20th century we might have 200 books...maybe I just answered my own question.
If they did constantly add more books, maybe just one every few hundred years, competing churches might have their own versions of what's canon.
Churches might become more hidebound, tied down to what's in their version of an increasingly long Bible. Or maybe not. I just thought I'd throw out the idea.
It wouldn't necessarily prevent abuses, but it would encourage the idea of a living, growing, evolving Bible.
And from uchronia.org:
McDevitt, Jack. "The Tomb".
Divergence: 312
What if: Constantine was defeated by Maxentius at the Milvian Bridge, leading to the complete break-up of Rome and a never-ending dark age.
Summary: C. 1700, a young man meets an old man excavating a tomb in a ruined city.
Published: In What Might Have Been? Volume 3: Alternate Wars (eds. Gregory Benford and Martin H. Greenberg), q.v.
I read this story; it implies that Christianity has gone extinct. But the characters in the story wouldn't know what happened to the Eastern churches, so they might still exist. They would have developed very differently.
To avoid the troubles in Europe, they might have expanded eastward, and the characters in the story would never know. Although, the Eastern Churches might have sent a delegation who make contact with the characters in the story the very day after the story ends.
The 1400-year dark age does seem bizarre.
What-if2 has a scenario with Jesus being pardoned, but the essay has Constantine speculating on the future development of the Church, which I found implausible. The essay doesn't say how the Church avoids the abuses of power of OTL.
It's strange that all 12 apostles don't have their gospels and epistles in the canon. If they had, that would have made a lot of difference...what the differences would be, I don't know. It might have been an improvement.
Certainly, getting rid of Revelations would be a big change.
One of the problems was the extreme sexism--the early Church leaders didn't want women portrayed as disciples, apostles or ministers.
Etruscans allowed more power for women in their society, so if the Etruscans had dominated Italy and the Mideast, with the rise of Christianity under an Etruscan empire, that might have helped.
And...
Ober, Josiah. "Not by a Nose".
Divergence: -36
What if: Marc Anthony was able to start his campaign against the Parthians on schedule and defeat them.
Summary: Essay which argues that Anthony's success in battle, and consequent lessened need for support from Cleopatra, would have enabled him to overcome Octavian. Subsequently, Rome would have remained governed by the Senate but would become bi-polar in its cultural development, the second pole being Alexandria.
Published: In What If? 2: Eminent Historians Imagine What Might Have Been (ed. Robert Cowley), q.v.
The essay has Cleopatra's successors being leaders of an Eastern Church.
Judas repents, becomes an apostle, his gospel is preserved.
Nicodemus' gospel becomes canon.
Nero impulsively makes Christianity the official religion, he declares himself the Second Coming, he orders himself killed so he can rise again, he stays dead, but the church leaders didn't really think he was the second coming anyway, but the incident makes them awfully careful about mixing religious and political power. Despite Nero's death, his edict making Christianity legal still stands.
An early general converts to Christianity, becomes emperor, it becomes legal much earlier.
During the Year of the Four Emperors, 69 AD, WI one of the emperors is Christian? What if the empire was divided four ways that year and was never reunited?