Winter campaigning

First of all, let me say how much I liked what I've seen so far - and how much I am looking forward in anticipation to the completion of this project!

I've seen somewhere (on twcenter, I think) a post about winter campaigning, but no answer to it from the team. As far as I know, fighting in Northern Japan was punctuated by winter season, when snowfall made Mountain passes impassable, and therefore any military campaigning impossible (for example, between the Takeda and the Uesugi).

Has there been any way of introducing this feature into the mod, and, if so, how did you manage to achieve it?