Byzantium should start with High Crown Authority

[LWE]

Although there is definitely going to be a further DLC to better represent the unique strengths and weaknesses of this Roman remnant, this is an obvious quick measure. There's no way Byzantine "vassals"/governors could just make territorial claims and declare war on each other like nothing out of ordinary is happening in either start date - its governorship was too centralized for that.

 

[Sleight of Hand]

The problem is, what do you then do as a Byzantine vassal? High CA was awful in CK2 as it made playing as a vassal extremely boring as your gameplay options were so limited - this was a problem England had after 1066 as the Devs gave William high CA.

 

[LWE]

I guess you could do external expansion (conquer lost lands for the Basileus), limiting your internal options to Byzantine plots.