Ashrem
Oh Wise One
Rather than shoehorning a future guest race into our cities, have the protal be the only manifestation of the race in our city. Let it be a portal for us, takes us to a separate server for the guest race, with a blank city that has an appropriately themed background.
Instead of incorporating all guest races elements into our city, bring only select items back to our cities. The Portal takes us to the land of the new race, instead of allowing them to visit our cities. There we have a mirror of our city's portal as the equivalent of a main hall for the new world.
At this point, we are working on two separate tech trees, one in our home world and one in our guest world, each progressing with it's own KP. stream. Let the world develop like a new server, and as people complete the chapter, they are slowly pushed to the outside edge, as each new player is inserted at the centre of the map when they open their portal. Don't make it a full world, where many people might want to keep playing, but give it a subset of the functions of the primary world. New provinces to scout, new neighbours to discover. Key technology points would be required to be met in order to continue progressing in the primary world's tech tree (Ancient Wonders, transplanted building upgrades etc.), but their whole city wouldn't to be disrupted.
Alternatively, have the entire tech tree take place in the other world, but the upgrades are applicable to the original world.
Instead of incorporating all guest races elements into our city, bring only select items back to our cities. The Portal takes us to the land of the new race, instead of allowing them to visit our cities. There we have a mirror of our city's portal as the equivalent of a main hall for the new world.
At this point, we are working on two separate tech trees, one in our home world and one in our guest world, each progressing with it's own KP. stream. Let the world develop like a new server, and as people complete the chapter, they are slowly pushed to the outside edge, as each new player is inserted at the centre of the map when they open their portal. Don't make it a full world, where many people might want to keep playing, but give it a subset of the functions of the primary world. New provinces to scout, new neighbours to discover. Key technology points would be required to be met in order to continue progressing in the primary world's tech tree (Ancient Wonders, transplanted building upgrades etc.), but their whole city wouldn't to be disrupted.
Alternatively, have the entire tech tree take place in the other world, but the upgrades are applicable to the original world.