Making a mod for the Western Romans to use Eastern Roman cites: please help

KVK

I might have posted this already by mistake, and if so I apologize; at any rate, I am having problems with the assembly kit. My idea was to make a (theoretically) simple exchange of city models. I want to make the Western Romans use Eastern Roman cities, especially in battles. After many failed tries, I came up with a solution: I modded the building_culture_variants file to have the western roman subculture use the eastern city models, including the description, picture and "flavor" fields. I also tired editing the start_pos_settlements file so all cities would start out as eastern roman styled, but for some reason that didn't work and I started with the default western cities (Which I wasn't able to upgrade, downgrade or see the pictures of, but I could convert into eastern roman cities). I converted them all immediately, and after some turns I had the first settlement battle in (what I thought would be) a converted roman settlement. I was preparing to fight in the new battlefield, when I noticed the map in the loading screen was oddly familiar, with a peculiarly shaped building at the center of the-
It loaded the amphitheater village. Again. Despite the main building being clearly an eastern roman city. I really don't know what I did wrong, and if anyone is willing to provide helpful advice, I'll welcome such insight with open arms. I have looked through any and all files which might have had something to do with settlements, trying key words such as cities, settlements, and subcultures, and I'm not going to make any progress unless someone can help me.