Since Elemental is planning to have a lot of resource types (i.e. multiple types of lumber, multiple types of metal, so forth) instead of having each one do something different all the time, you can have it so multiple resources of the same category give bonuses to production. For example, 5 lumber mills producing 5 different types of lumber (i.e. Redwood, Pine, Oak, Palm, etc) would be more efficient than 5 lumber mills all producing pine. That way, there is a use for different resources even if they are just variations of each other, and each wood doesn't need to have little micro-effects or something.

Anyways, I'm still in favor of exotic materials doing exotic things. Just thought that would make things simpler for more mundane stuff.