Let's start with the bad news. I researched what would be required to get the game to support multiplayer, and realized something. In order to have network multiplayer, I'd have to restructure the whole game to work with it. Since I've never experienced programming with networking, I can't accurately estimate the time required for such a task. So the plan is, the game will remain single-player and hot-seat multiplayer. After it is released, if there is sufficient interest in network multiplayer, I may work on that. It depends on how much effort it will require, and players' interest.
However, the save/load will save all changes in your current turn, so you could have a hot-seat multiplayer game, save at end of your turn, then email the save game to the other player. It will be basically PBEM (Play by Email). I will see if I can support that a bit better (forcing you to quit after your turn, password to enable start of your turn, or something)
Now, for the good news! I researched into AI programming, and realized that I can do something that programmers will love. I can have AI scripts in either C# or Visual Basic, and my game will compile them, then run them as third-party DLL. So the game's default AI will run from a script, and you can see the structure required to create your own AI. So if you think the game's AI is weak, you can create your own AI! The game will pass in critical data to the functions in the script, then expect certain data in return. What happens in the middle is up to you.
I plan on implementing ability to watch a game if there's only AI players and no human, so you could set up a deathmatch between different AIs and see which one is the best :)