Also, we've made some game play decisions.
-Merchant, engineer or generally scientists players are scratched. They never did anything anyway.
-Resources, trade and businesses have been highly simplified: resources give a price reduction to certain units and buildings (namely, -1d to the price). To gain a resource, one must either exploit it or trade it. To exploit a resource, one simply needs to make a business for 3d based on a resource naturally present in the kingdom. Afterwards, this resource can be used by the kingdom. Resources can also be traded: by simply establishing trade routes between nations, said nations can exchange resources. Once the trade route is established, both nations have access to both resources. A resource can be used in production and in trade at the same time, but it can only be traded to one nation. Some nations may ask multiple resources for another (example: cattle and grain for HQ wood).
The noble having established the trade route gets 1d/year from it, due to trading taxes.
-Nations are now much larger and contain more parcels and cities. To balance this, there are now landed nobles, and the king only receives a certain percentage of their money. This system should reward good kings, who will have the support of the nobility, and punish bad ones. As much as possible, the nobles will remain undefined in order to make the GMs' job possible.
-One of the main things in the Middle Ages were castles - well, we'll add that in. There will be three levels of Castle: Level 1 grants +50% strength to the defenders, Level 2 grants +100% and Level 3, +150%. Basically, Fort > Castle > Citadel. Cities may also build walls, for half the strength bonus and half the cost.
The cost will be as follows:
1: 3d, a season to build
2: 6d (-1d if Stone is available), half a year to build
3: 8,5d (-1d if Stone is available), a year to build
Catapults still give flat bonuses, since they require engineers. Siege towers lower the strength bonus by 10% each.
-Armies will now have the possibility to outmaneuver each-other if the leaders so desire. Two armies maneuvering or racing towards a position will roll against each-other; highest roll wins. Large armies get a penalty to such movements: -1 to the rolls for every 5 regiments above ten. This is to prevent war to simply be "Make one doomstack, curbstomp everyone".
Comments or suggestions?
Also, although traders and scientists are scratched, you can still be another kind of non-noble character (mercenary, duelist, assassin, spy, whatever), no problem.