A mini-suggestion I came up with while trying to keep up with fast mode: A pseudo turn-based mode using a new time passage button. (In addition to the pause/normal/fast buttons we already have.) Making a truly turn-based variant of the game logic would probably require too much rework to be viable as a toggle at this stage of development, but it would be cool to have a button that would advance to the next "turn" (day? week? configurable?) while keeping the timer paused after the button press. A fringe benefit would be that those who continue to play in real-time mode would be able to quickly skip through slow periods of production or other empty weeks.
Interesting... I wonder how much of the internal code has changed since then. Personally, as a coder, I'd love to mess with the time buttons to see if I could make a turn-based mod for the game. However, I don't know if there's any way to re-compile the dll without the original source code, so I might be stuck with wishful thinking and/or making a similar system and playing with that.