Got to thinking, and I'm sure you've considered this as well, but wouldn't the game be cool if you could indoctrinate some of the hostiles some how. A few ways I could see this working would be either finding "lost children" of said species, capturing them and breaking their will to fight you, or trade. The lost child option could be a matter of the child version. Of the other races being a super rare spawn in the wild, while the "capture and enslave" feature could be a matter of having a cage built to keep them locked up for x amount of time which would allow you to then knock out enemies instead of just killing them. However, the trade option (which I'm only coming up with as a third option) could have you trade basic goods between the desired tribe. This option could introduce the idea of specialized units, slowing you to have hunters, gatherers, or trailers while still having room for even more specialized members of your tribe. Marking two different members as "nanny" could cause the two (or more) to try to reproduce, while the cook could be the one that goes from each member ensuring that they have food. These are just some of the dozens of ideas I have, and if any of them sound like they would fit in your game than by all means use them. This is a game I am excited to see finished and if my ideas can help than please let me know... Side thought though, will this game have magic in any form?