I'll add my usual CA hammering. Those dudes are just a few lazy bucks out there, governed by modern day profit thinking. They will milk us 15 dollar each for 1000 mini campaigns to come that add nothing else than a new / old map (which takes no serious dev time at all and no innovation process involved). They get away with it because 1.) people find history interesting and are fascinated by ancient story lines and will buy DLC's to play with their favorite general (caesar, hannibal, alexander the great, mark antonius), 2.) nobody kicks their ass. We have yet to see a competitor about this genre of computer games.
However they will NEVER do anything that takes manpower and time, but doesn't bring income (thanks for caring about the fan base CA). Hence they say the engine would be able to handle seasons effects. OH YEAH, we believe you CA... We live in the 21th century, were modern day wonders happen every day and people do things that were thought impossible, yet those CA dudes can't add seasonal effects to a computer game map... nor create a better and more practicable UI, add a family tree, make civil war something less boring and innovative, fix their bugs, improve performance, make the AI think, fix collision mechanics and blobbing, fix their particle effects, remove torches, enable a real buildings system, give us mapping tools, fix broken links in the db that renders no effects at all and not even the easiest to fix thing removing the "magic" round spotlights that appear over each unit when fighting at night. lol

and they get away with it... the world is a sad place.
And last but not least, Dresden and Co. already added seasonal vfx effects to the campaign map (snow effects, rain effects, water reflection on the floor when it rains, added plenty of new seasonal anomalies like scorching hot summer to the grande campaign, linked each single region of the map to a geographical climate zone (north, south, mediterianian climate etc.) with its specifical weather, weather anomalies chances and bonus system, integrated the terrain files and weather definition files we have from CiG. NOW tell me what the hell would the engine not handle? Some green leaves effects for spring, some red-ish trees and yellow leave effects for fall and some white trees and snow on the ground? How hard could this be? I mean all the calculations, probabilities, anomalies, dice rolls and effects have been implemented by Dresden with alongside some weather definitions and vfx effects. Other modders for example made clouds in the battle maps moving and rotating, created plenty of new vfx effects and wind definitions, a new lighting system and added autumn (red-ish trees and falling trees on the ground) for the battle map. I myself would assume the battle map is more resource intensive than the campaign map. Another one didn't like CA's shader and implemented his own... etc. etc. etc.
Now make up your mind, if seasonal effects are impossible or not.
CA bashing ends here, over and out!