Hey i just wanted to come through and say this game looks like one hell of a project and looks downright wonderful.
I have also created an inspiring "instrumental song" to inspire here https://youtu.be/6dRroLrkthk
Few suggestions
1. make the voices from populous multiple by sampling the voices from the characters and by then upsampling or downsampling the pitch ranges, to simulate a changing response when the followers speak.. or a simple filter so it changes by like 3%
2.also you could sample new samples sounding similar, with other voice actors, and then bind them together blended 60 40 or something to give it better 3d definition.
3. try this. take the stories from indian folklore and apply each story to the levels as a info source. we can draw the stories from navajo, catawba, iroquois, apache, cherokee, hopi, blackfoot ecetera... it could cure a writers block
id love to compose or try to come up with some level ideas to contribute but if i will it will take some time as the inspiration, absolutely has to be there