Here's a list of things that need to be done for the mod to get finished.
Update to the newest version of the game
New events for the new religions
Are the discoveries still done?
Province names should be changed to something more contemporary. (Mostly undone still afaik)
History fixes. For now all I can say that the Scordisci are missing. There are likely a lot more mistakes, so you could go though historical maps and compare them to the AT start setup on that date.
Here's a list of things that need to be done for the mod to get finished.