There's a lot of interesting stuff that could be modelled in the world of cyclonic weather and weather scenarios... namely tornadoes and hurricanes, but also things like weather mod and the ability to launch weather balloons?
This alone would create all sorts of possibilities in the world of scenarios. Think of a data mission into a hurricane... and being able to see the inner eye-wall once there? Or dropping catalyst crystals into clouds to make rain? Or having to deal with TORNADOES?
After all, this is, in the end, a simulator of the atmosphere and everything in it.
Among everything else in the sims so far, I would argue that simulating the SKY is the one thing that [they] can still do the most with. We have autogen... we have water effects... we have ground shadows... and we have a pretty good sky, but it could be a GREAT sky!