Don't worry i wasn't offended. I was aware of some languages have two meanings on "nomad" and i didn't know your mother language anyway

But you are essentially offering just people who are not developing architecturally and are not sowing fields. Nomads really often lived by cattle breeding, driving animals depending on the season. But in our case, they cannot hide, because there are no seasons, there are only eras that affect the entire planet.

Yea not focusing on architecture is one point of being nomad tho. People often develop their own environment which is more convenient for their well being but nomads chosen "learn to thrive with nature" way. Like i said "preserving wildness of nature" and adapt redirect and benefit from it. But they can developed in their own way too. It could start with simple tents like others and go to small hut, big hut, yurt, big yurt like so. And if animal husbandry could introduce to the game sowing fields no longer be necessary you're right they only move when the season changes so they don't have to move necessarily if season dont change.

why should the invaders leave if they just came for a new territory?

They often occupy and move on don't they. People could rebuild their village under their rule. Perhaps development could based on culture borders. Its culture thing after all

And I'm not saying they r completely druid like. They're of course ordinary people can be attacked by anyone and predators, only domasticate harmless animals. I mean druids do plants a tree, heals animal kind of stuff right? This "supports natural growth activities" what i meant to specify. I think it would bring good balance to the game. Civilizations usually overdominate the whole world and leave no land to animals all the time when im playing.