To do it properly they need to be willing to move and rename the maps to be more accurate and make room for new ones. For example, the Plymouth map doesn’t even contain Plymouth. Most of Canada is missing because of the distorted map and South America has a pretty odd selection of areas represented.
For native sites, only South America is in urgent need of new content. The addition of Tengri and Sufi rework fixed the worst of the problems. It would be nice if they made a new home for war elephants and added a Bedouin option for Africa and western Asia. Inuit could also spice up the north. A few others like Habsburgs need a rework for their units and techs.