Some good ideas Tyranick,
You will some races do better in certain lights, and weather effects than others, and certain ones do worse. Even more so, there will be different effects for different unit types as well, for example, a heavily armored unit like the Human Thane is going to be hindered more by snow, than say an archer who is lighty armored.
Destructible land is something I wish we could put in, and it's something we've experimented with, but the strains it puts on system resources are just too great at the moment. We'll have to wait for DoF2 to have this feature put in, when hardware is readily available that could handle it.
We do have Hero units, in the single player campaign you will have heroes for each of the races. In the MMO version of DoF, you will actually get to create a hero to represent your army.
I personally haven't played Rise & Fall, so this mod isn't something i'm familiar with, if you could explain the concept I might be able to answer the question.
Expected release date is Q1 2008.
Environmental effects will happen with certain weather conditions, or some will be magically induced.
Glad your looking forward to it!