It's possible, to replace a culture, because the Africa-Culture is the same as the Egyptian-culture, so that you can replaye one of this. The problem is, that you need new buildings für a new culture, who are saved in the AllMeshes.g3d file as l3d-models.
The first prlbem is, that no Programm for the l3d-models can save the textures correctly, so that the game can crash, or the objects are invisible.
The second problem is, that when you want to add new objects for your new culture to CI, that the extractor/compiler for the CI-Version of the AllMeshes.g3d file is buggy and doesn't work.