Samloyal23
Adventurer
"Byzantine" is used to connote complicated schemes and political games, a baroque level of urban plots. Spies, assassins, merchant princes, and other city-based characters and plots should be emphasized...
Byzantine politics was actually not that complicated or baroque, it just looked that way to the Western Europeans at the time used to relatively basic levels of bureaucracy. But you could certainly have scheming eunuchs and nobles if that would add fun to your game.
Instead of Theodora, have you thought about using Zoe and (a different) Theodora as your rulers? Two sisters who ruled as co-equals but who really did not get along. One a bit wild, prone to bad decisions and power-hungry and the other who really, really just wanted to retire to a nunnery.
One of the political factions wants to "restore the grandeur of the Empire that was" and advocates for expensive open-ended campaigns to reconquer former provinces. This group might hire the PCs as an information source and also to tackle problems in the province, to make their goal look more easily achievable.