I understand the benefits that can be provided by having different materials, like wood, metal, stone. Just as you could have, instead of food, cereals, livestock, and fish.
The more resources there are, though, the more difficult it is to balance, and the more effort is demanded from the players to manage all of it.
My proposition was for 1 important resource (food), one useful resource (materials), and one luxury resource (goods). That way people can get away with continuing to manage just 1 resource without crippling consequence, or deal with two to optimize efficiency, or deal with three to maximize everything and make more profits.
If you blow up the resources into wood, stone, and metal, then instead of doubling the number of resources you need to manage to run everything smoothly, you multiply it by four. Lots of people hate the trading game already, and as such I don't really think that quadrupling the amount of time people have to spend on these (and more, since these resources probably won't be as common in all realms as food) is going to make things more fun for people.
