The concept  was mentioned before. A Neutral building is non-buildable structure and don't  the architecture influence by any faction, isn't relative to any, is only a usable building if is captured by a player. in this new building you can train eyecandy units. slaves from all cultures. Men and women. This will be cheap than current villager. wild animal (tamed) to use as pet or to fight, like tigers, lions, elephant workers, war dogs.   Examples