As i wrote in toher posts:

should be added a resources and rare resources system for buildings (wood stone and more else...) for increase trading and wars.

And this will be an exaple:
Roads 20 stone *
Farming 50 wood *
Animal Husbandry 80 Wood *
Port 100 wood 100 stone *

Forge 300 stone(and maybe divide stone and wood)
Castle wall 400 stone
Horse breeding 400 wood

Cost of resourcers is around 1/3 of silver cost (that should be added at these material costs) except for ports, lesser ports more tactics.

We can also added some rare resources, for example Forge should need some Coal and/or Ore (50 or 100)
Should be nice too have more kind of buildins that need silver+ some rare resources (for example wine or incense or hide)

this would be interesting cause many nations will need more resources that will be more difficult to find!
And you should choice wisely if use for buidlings or for bonus in battles!

I suppose add new buildings and new effects is a bit complicated, but at least add use of normal resources (wood and stone currently useless) for build currently shire buildings shouldn't be too much difficult or longer!

*Road Farming ,Animal Husbandry, dock shouldn't have a cost in capital shire, that's why new nations can grow fastly.


Which is the purpose of this?
1) Use unuseful resources actually as wood and stone
2) Slowly fast rebuilding of structures if you have no resources left
3) Increase WAR for conquer RARE resources, actually them give only a bonus to fight, but if you need them for specific building with some bonus many will trade or try to conquer that's shire.