Mr. Jay,
Dare I ask why you are thinking of making the Byzantines Independents?
I strongly think you should make them, not Independent, but the Roman Civ. Or, possibly, the Greek civ, but Rome preferably.
The name 'Byzantine' did not exist until well after 1453, when the empire fell. The Byzantines throughout their whole history referred to themselves as one thing alone--the Roman Empire. They had political continuity with the empire, and had never fallen, unlike the western empire created after Diocletian's partition. (Europe tended to call them the Greek Empire in contrast with the Holy Roman Empire, and since the Byzantines culturally kept more of Greece than Rome).
The Byzantines remained a tremendous force for quite a long time and effectively kept the Arabs from sweeping into Europe. They did the same for the Turks, at least for a long time.
They were a unified state with advanced technology, and for a long time were far more 'civilized' than Europe.
For those reasons (and because I want to play as them
) I think you should make the Byzantines either the Greek or Roman civ. Rome is more historically accurate, Greece makes sense too since their heartland is the Byzantine heartland as well.
I also think the AI (Arabia, Turkey, and Russia in particular) are more likely to go to war with a full civ than the independents. It also means the Byzantines will have a chance since they won't be bogged down with maintenance from cities such as Pagan and Chichen Itza
. And the Byzantine military held its own for a long time!
And eventually it will collapse--Arabia should conquer Egypt and usually does, Turkey will spawn and take... Turkey, and be a step from Constantinople. Rome itself, which they held in the middle of the 6th century, will fall to barbarians before Spain spawns, I imagine.
At the height of Justinian's rule they held Carthage as well, and even SE Spain. All this maintenance will keep the empire slow to respond, as it should be. It should be strong, but not able to compete technologically with Europeans or Turks, I imagine.
WHOA rambling. Anyway, that's my pitch to make the Byzantine empire belong to its political or cultural forbears (Rome & Greece respectively).
Plus it saves ME the trouble of making this a scenario, which I planned to do and probably will eventually. But I think your project is great and as such want an interesting Byzantium! Vikings even served there as mercenaries.
fin
I just haven't had the energy to sit in fron of the computer... 
