I don't see what the problem is with creating a more local RFC. Tbh, from examing mayan history, I think it may actually be feasable to do an RFC Yucatan simply because of the numerous polities that are difficult to represent in the mod I'm working on. The same is probably true with southeast asia in RFCA. If the history is rich enough, there really isn't a limit to how local the map can get without losing gameplay or flavor.