Re: The Role Play Forge - RP Creation Teamwork
Those three tribes definitely sound good, I would stick with those and leave it at that. Adding more probably isn't necessary. And I agree with you that the RP shouldn't be only about fighting, but as we all know, every war has its battles and its moments of ceasefire as the sides prepare for the next engagement. I wouldn't worry too much about being concerned the fights will be seemingly endless.
You could also have it where you have RPers taking on the roles of the natives as well. This is a pretty flexible idea, and you have the option to open that up any way you like it.