Production and exchange of resources

Mercantilism is founded on the exchange of goods, which are produced by provinces specialized in particular resource.

If we think the entire Kingdom as one single organism wich have some cells that produce and exchange resources among them, we understand that be specialized in a determined production of resource strengthens our economy.
For example, an acre of bank in a merchant province, with lots of alchemy science can have 50% more efficiency than this same acre in another land. This other land could be producing some other kind of resource to exchange by the gold produced by the merchant.
There are 4 kind of resources and each one has a trade value:

• Gold: 1gc 
• Runes: 3gc 
• Food: 0.05gc
• Soldiers: 100gc

Gold: Produced by banks, peasants, prisoners, increased by alchemy science, merchant personality, build efficiency and possible some race, also can be generated by Tree of Gold
Runes: Produced by towers, increased by channeling science and possible mystic personality
Food: Produced by farms, increased by food science, shepherd personality and build efficiency
Soldiers: Determined by the draft rate based on the population, increased in 30% by patriotism, and has their cost reduced by armouries and possible some race or personality

Depending of the characteristics of each race and personality on each age, some king of specialization will work better or worse.
For example, when mystics have double production of runes, 3 or 4 mystics can produce runes to the entire Kingdom.
Humans, or Faeries merchants always can produce large amount of gold.
Dwarves can focus on gold, runes or food with their bonus on BE. If shepherd personality is availabe can be a good food productor.
Attackers that are always training troops with good amount of armouries can produce soldiers with a cheaper price.  WHen orcs produce free soldiers, they should always keep the draft rate on emergency, keep patriotism active and exchange this precious resource with the entire Kingdom. 
Rogues should be always looking for resources that are missing on the kingdom, feeding the kingdom with what is demanded.

Maybe a problem is the unbalanced trade value of the resources. While gold and runes are ok, food has without doubt a very low trade value, and soldiers probably too taking into consideration the difficulty and time in producing soldier.
For example, if you ask for 100K gcs and want to pay in food, you will need to send 2 million bushells!
There is another problem in make specialization on food: A kingdom need to be extremely active and organized to make the food reach the lands that are not self-sustainable on the right time to not cause starvation. 
For these two problems, the food maybe should not join this strategy, but still we can have some provinces producing a surplus of food to shortage time. 
Here a table just for example of how exchanges can work

The attackers feed the entire Kingdom with soldiers, the mystics helped by the sages produce the runes needed. The merchant helped by the sages produce the gold. Also the attackers can run a litle less farmers and be aided by the sages. The surplus of halflings actually is not of production, but product of thieveries, that can help the kingdom with what is missed.