As described in other topic the game will be played on a supergiant Europe map. Later I maybe add the New World too and if players research ships large enough to carry people + resources for such long sea travel it doesn't have to be a spanish hero who discovers America this time.
The game will run continuously on a server and when player connects he will get updated status of his kingdom. Some tasks requiring instant player interaction (for example farm seeding) are removed and for others like units training, army movement or building you can hire an assistant who will execute your orders when you're offline. For buildings you can draw your floor plan, assign builders and let them build your city layout while you're away.
There are still crucial cases like attacking a city of an offline player and i'm thinking about the need to declare and accept a war before being allowed to attack a major city of some player. You can still cut the supplies or raid the surrounding agricultural area, but if you attack the city some Central Authority will help to defend it. Or maybe AI can handle the defense.
New players will be able to join the game if there are still free starting locations.