I’d say, make (Elite) Steppe Lancer available for Byzantines, let Logistica affect regional units as well, make Bloodlines available for them, but take away their Camel unit lines.
This game has never put historical accuracy over gameplay and balance, that said the byzantine empire extended into egypt and did use camels. Furthermore giving them bloodlines is a massive overbuff
I know, I’m just trying to fix Byzantine cavalry line which is not so impressive right now imo. Their Catas hardly see any use outside countering Infantry focused civ, and if they face spams of arbalesters they’re pretty much finished.