Just a quick fix I made for myself with BFTB2 in case anyone else was interested. It changes the Byzantium faction into the Eastern Roman Empire, changes all cities and castles names,naval units, task and combat descriptions changed, all relevant campaign descriptions, and unit cards and ancillaries changed so they all direct towards the 'right' name.
As always, make sure to back up your files in case I'm an idiot. Just drop:
*Export_desc_ancillaries into your Data folder.
*export_ancillaries into your Data/Text folder.
*export_units into your Data/Text folder.
*Expanded into your Data/Text folder.
*Campaign_Descriptions goes into your Data/Text folder.
Spoiler Alert, click show to read: