What if there was seasonal shift every turn, for example 4 turns is a year. And this has consequences on the map like no going through antartica in winter, or no connection between Alaska-kamchatka. Is it crazy? too complex?

Why? How does it add any fun to the game?

From the realistic standpoint, I don't think Antarctica would be hospitable in any season; that would be a job for a tech tree if it really needed to be solved. The Bering Strait being impassable during winter sounds correct for the real world.

If too many of these modifications are added, WarLight will be a Web clone of Sid Meier's Civilization rather than RISK. ;)

Additional thought: That would be *a lot* more work for map designers, and would only apply to maps where the designers had used those features.