I love the idea of faster moving on roads and slower movement if not. It seems more immersive, seeing as roads are of course one of the main indicators for where you're going, how you're going to get there, and when you're going to get there. I mean, if you're driving on a car and wanted to go somewhere, let's say 10 miles away. Would you use intersections, and side roads to get there, or would you use a highway? It seems like a no brainer to me.
A speed penalty depending on the season (no doubt it'd be during winter. I mean, what's going to stop you during summer? Blooming flowers?) would also be interesting. It'd allow for an even more pressing push to use roads. However, this could be taken advantage by the player against caravans and unaware armies. Of course this wouldn't be too "good" for lack of a better word. I personally would love this to happen in game. In Mount & Blade: Warband, I absolutely dreaded seeing roads leading to other cities, but clicking on them would cause your character to just run straight to it, rather than using the road. It made the roads redundant. However, if this new road system is implemented in Bannerlord, it'll definitely reduce that redundancy, and cause using roads (especially during the winter/snowy months) to be used more necessarily.
~ Ser Tariq