Why have 10000 resources? Just have 3: Food, Materials, Goods.
This approach has some instinctive charm to it due to its simplicity. Each of them is valuable on its own, each of them accomplishes something meaningful and each of them is straightforward enough to easily grasp. The peasants need food to live and breed, materials to make stuff and goods to make them happy.
There is, however, a way that we could expand the "Materials" resource to comprise of a variety of different kinds of materials. For the sake of simplicity, all materials would accomplish the same. You could have wood (forests), stone (mountains), metals (other mountains) and perhaps even exotics (in small quantities in desolate regions). But if you had more variety stored in your region, less of them would be needed in total.
Say you wanted to upgrade your fort. If you had no materials stored away, let's say the upgrade would cost 1000 gold. With materials you could have 80% discount. So you buy 200 units of wood
with 100 gold, which saves you 100 gold in total.
But let's assume that you buy 100 metals and 100 stone instead. That is 200 units of materials in total. But because having more resources present uses less of each, you would use only 50 metals and 50 stone, so you would actually need to buy only 100 material units in total, saving you 150 gold.
Further, if you bought metals, stone and wood, the amount you need to spend each of them falls further, saving you more gold. So, the more you are willing to work to keep all kinds of materials stored at your region, the cheaper it would be for you overall. Missing one or two resources would not be fatal in any way, as the others would compensate, but those willing to work for the variety would reap the greatest benefits.
In some geographical areas some resources would be more scarce and thus more desired, and would have higher prices. Where there is excess, it would be sold towards the needy regions. Regions in between would profit as trade hubs. Some realms, such as perhaps D'Hara in Dwilight, could truly become realms specialized in trade.
If materials effected the regional production directly, the system could work the same way. To gain the materials bonus, you need to have some materials available. But if you have a variety of them, all types are spent but the overall amount consumed is reduced.
This way there is no need to limit the variety of different materials that are produced. You could have three, you could have thirty. They all work the same way and the only thing that matters is to have as many kinds of them as you can. This would make it possible to make the trader game more exciting without making it any more complicated for the player.
Ps. the numbers I used are mock numbers meant to illustrate a point. The benefit of multiple resources should probably not be quite that strong.
