What type of pack?
I've had an idea of making a pack that is completely different from what the simulator is about. It's a dungeon boss fight, where you, the player, chooses a weapon (development level) and defeats the boss. Ooh, I just came up with something. You pick your weapon, and progress through the actual dungeon. (progression will be represented by taking cities)
Another idea is to create an expansion pack for the original game like praiseDog suggested in the game description. More events, thorough description, etc.