Good point, but one famous instance of fighting in Autumn was Hastings. Stamford bridge was fought in late September, before Harold marched south to face William on the 14th of October. While there were problems for Harold with some of his men already having gone home at the start of September to bring in the harvest, he still had many soldiers; perhaps some of the fyrd that hadn't previously been readied for the expected invasion of William were called to the army when the first lot were sent home. William had brought across an army of several thousand men and had been trying to cross for one and a half months by the time the weather was good enough.
So there are examples of large armies operating at harvest time. But the point I was making in the first place was that the winter should have an effect on the viability of campaigning, not make it impossible. I hope that as well as the weather effects, there is also some sort of feudal system, but I think it might already have been said that the recruitment is the same as in Warband. It would be good if you could take out half a village's levy for the summer and half for the Autumn, say, which would allow a modest army to be used up until the onset of winter. One of the good things for me about the Battle for Sicily mod, which I played on M&B .808, was that as a lord, your village levy could only be kept out a few months at a time, or it might even have been a few weeks. You could have your knights with you as long as you wanted but the levy had to go home after a certain time.
Like I said earlier in this post, I think they've indicated that the recruitment will be the same as before, essentially buying troops from any village. That would be a shame. In a way it makes sense; if you pay a young man to join your army and pay him a regular wage, he may well be richer than being a farm hand on a large estate or tending his own small strip of land and thus eager to join you, but there are issues with this that aren't represented in Warband. The reduction of manpower should badly effect the productivity of the village, reducing the amount of food and other raw materials harvested by it, making them scarcer. It should also anger the lord of the village, since you are making his source of income less productive.
I would like some factions to have a feudal system, where levies are called up to form large armies and only have to be fed, not paid. You could keep a retinue of professional warriors such as knights and sergeants with you at all times, paying them, which of course you could also do with mercenaries, but the levy would have to go home after a while. The Empire could be different though, perhaps maintaining a professional standing army (if we were to take the very early Byzantine model or late Western Empire model), which would cost a lot of money but the troops would all be well equipped and never need to leave the army to run farms or businesses. It would give more character to the different factions and make the world feel more alive.
I'm fairly sure it isn't like this in Bannerlord though; Lust said in the Q&A at the Weekender that all the factions had a king with lords beneath him and I think they probably all have the same system as one another. Of course we have also seen that a player can have a mixture of faction troops in his army, so clearly the player doesn't need to be a lord to recruit villagers. Still, it will be interesting to see exactly how recruitment works.