A multi server system could work quite well for you. I had plans with McTwist to link multiple servers via tunnels and metros for our city rp build so we could have a larger city. We would have use events to connect to a specified server when a brick is touched. Here you could have a desert area be in one server while the capital city is in another.
I was wondering if this would be a good idea or not. There will be a lot of traveling here, and traveling between worlds to find different things is important. With the data and stuff, i'm not sure exactly how syncing it between servers would work. I'm not sure if it would slow things down having to send the data through some other program or something, and it's a real pain as a player dealing with loading screens. I don't want people to be discouraged from exploring and going back and forth between worlds because of the obnoxious loading screens.
Working with multiple servers is important when making an actual MMO, but I don't know how well it would work in blockland. When making an mmo, you can make it seamlessly transfer from one server to another, you are in control of how effective that works. Here, we have to deal with the existing framework of the game.