My essay about Alternate History (Adderall and Summer.... strange brew....):
Alternate History is total bunk, let's just go ahead and say it. Mad respect to Dachs, and I understand how Dachs uses alternate history to both practice and show off his knowledge of the tiniest historical details and also his knowledge of the mechanics of historical progress. But it's all bunk, it is all by its definition implausible. The South did not win the Civil War, the Reich didn't win the Second World War and Hellenistic Culture took a nosedive after nobody could hold Alexander's Empire together. I do not care how many nails you are willing to provide, the kingdom will not and cannot be saved, and it is fiction.
Having said that I greatly enjoy alternate history and have for the better part of a decade, I have dozens of books on the subject. What I find interesting is not the minute historical details (Although if you look at, say, Ripper or Pax Germania you can see that I do take care to incorporate such things as a gesture of goodwill to the genre). My whole style of writing instead is focused on setting, and on creating a total world setting because the world creates the characters and defines them. Alternate History provides a lot of ways to play with the setting in radical ways and bring up interesting perspectives on race, nationalism, and even (if you accept my "product of their environment" thesis) human nature or (yes, Dachs) History. People can nitpick but at the end of the day your timeline is no less plausible than
The Man in the High Castle or
Ruled Britannia, but again both Mr. Dick (R.I.P.) and Mr. Turtledove understood that they were not creating a timeline for a timeline's sake but in order to create a compelling environment for their characters to behave in ways that simply aren't plausible without the divergence (Shakespeare writing revolutionary propaganda? Factories mass producing fake Civil War relics?).
Now to my notes on your timeline specifically. I find it a little too Eurocentric. Frankly instead of Rome I would go with China, even before the Treasure Ship fleets it's a more plausible sail (up North, running along the coast and BAM, admittedly the Pacific is a beast, but IMHO China getting to the new world in a sort of pre-Treasure Ship prototype is more plausible than the Romans getting there).
I think it would be a more entertaining world to watch the Chinese, the Caliphates and the Tribes dividing Rome into spheres of influence. Then the divergence is simple, no Mongols. But I also do not believe that the administrative structure of Rome was up to the task, it was high on ambition but also at the whim of people like Nero and Caligula who, I'm willing to guess, mismanaged things a little in the bureaucracy. You either need a stronger Imperial Succession for the Ceasers with fewer cases of adoption, in which case Christianity couldn't have gotten big in Europe so that people were willing to worship their God King rather than be 'citizens' of a 'state' with their own personal beliefs. The other option is probably to keep the Republic and change whatever the hell you want based on the reforms of 44 B.C. and then just say Democracy Rulez if anyone tries to give you any crap about it, and the new meritocratic Republic, while probably not as large or aggressive as its imperial counterpart, why not say it has more staying power? If it makes a good environment for your characters to play in that is what is important.
But either of these serves to make Rome less central and I don't know, maybe you're going for a Rome thing.
Trust me, I've been there myself.
This is probably no help to anyone. But that's what internet forums are for. To be completely unhelpful.
