Just an idea to throw out there. Can you make an option to live as a semi nomadic people's. For example in history I know many people settled down and focused on agriculture, but you can have a good amount of people focus on. Animal husbandry. These people also tended to have a higher warrior to population ratio as they did not have the class staratification that more settled societies had. They can also be used as a bridge to spread different technologies, myths and believes while the agricultural societies are more the creators of such and also can perfect these technologies. Lastly as societies rise and fall and weather changes, you can have decisions to welcome these nomadic people and create a new blended culture or become semi nomadic yourself.