I think i've experience a similar situation where heavy snow was followed by rain. The foot units crawled. But then all of them were exhausted, so i'm not sure how much actually was due to weather conditions.

Another key element of the english victory was the improvised pikes used by the longbow men. Would be nice to have those in the game.

I have seen many references of agincourt in litterature, but does anyone know if the battle has been filmatized?