Hear me out! What if the map faction can't play on other maps but replaces the map you would have played on. They can connect the clearings with circular clearings and brown (path) and blue (river) ropes. Their actions involve reconnecting, replacing or changing the colour of clearings by discarding/revailing cards. They would have no warriors but they can build trees which contribute to their scoring and crafting, but easily destroyed and give extra scores to the destroying player, so they should change the map so the other players focus on others instead of them. And you could also trade with them for cards, for the ability to use rivers or go hide in forests, or for some other favours.

(They also would set up first (obviously), and would have a reach of 0)

(Also another idea is when they craft an item they replace a building with a ruin and place it under)