To implement season is a great idea. And would be awsome in Elemental. But i'm afraid that the coding that would have to be done for that will possibly delay the progress of Elemental. There is a lot of factors that would have to be changed...
I think i would go crazy if the map changed for each turn.. Maybe if the season changed after 10, 25 or 50 turns it wouldn't be so bad.. But what about the sovereigns age.. That would probably affect his/her aging...
The graphics for the buildings might have to be changed. Like, during winter it would have to be snow on the roof tops and stuff like that.
It probably wouldn't be impossible. But i think that would require a lot of extra work, and would have to chang some of the allready written code of the game. I don't even know if they would have to change something in the core game engine (probably not). But yea, this is just my opinion on it.. Great idea, but it will require a lot of extra work!