Will their be a seasonal change added to the game, in terms of weather. Having seasons change or specific industry having to shut down during certain seasons can have huge impact on progression.
Fisheries - would be impacted as water temps change and fish move away to warmer waters.
Farming - hard to grow food from frozen ground, silos/granaries for storing food for winter.
Carpentry - Reduced tree cultivation during winter months.
If heating/cooling players housing was an implemented mechanic, then Coal would have a huge part to play in winter seasons as the build up of smog from coal burning would have a large impact similar to real world. This could mean that more efficient wood burning or electric heat could be used.
these are some ideas/examples.