I'll gladly put up the source code and walk anyone who's interested through it. It's pretty simple stuff, for the most part. Feel free to incorporate into mods, apply to different settings, tinker with behavior, etc.
Basically, the caravans go straight from A to B. The guards have a few variations in their actions depending on how close the enemy is.
The raiders don't target the caravans specifically, but until they're on the enemy side of the map their aggressiveness is set to very low, and they aim for the midpoint of the caravan route. If the raiders are wounded, they retreat to the caravan destination to heal.
There is no AI mesh for the desert map, although one would probably help -- assuming it covers the whole map. If it only covers part of the map, it will create complications.
I didn't add in too many scene props so as to keep the map big (which I like) and no stress on low-end machines.
For villlage raid mode, I was thinking that you would break into animal pens and then try to escort animals to your side of the map. Herding would be simplified -- stay close, and they'll go the right direction. Villages would have alert levels that would draw defensive patrols, so if raiders hang around too long they'll get overwhelmed. Torching a la Vikingr could be added for extra mayhem.