I suppose much depends on how much importance you want to give to the resources. The more important they are, the simpler the design ought to be. If the resources are both important and complicated, it forces the game towards TradeMaster, as it is economics at the end that wins wars. If they are, instead, of marginal importance, some players may choose to dive deeper to the nuances of the trading business but it is not absolutely essential to do so.
Personally I don't mind either way. If trading were to grow in importance I know I would enjoy it. But I am not so sure for the majority of the players.
As for the actual uses of each individual resource, I can imagine it would require quite a bit of careful balancing. Should each resource have roughly equal demand in average game environment? How much and what type of resources does temple upgrade take? Roads? Tournament Grounds? Recruitment Centers? Do archers take more wood than cavalry does? All that has to be thought of, balanced, tested and adjusted. Some realms may gain significant advantages over their neighbors due to controlling a key resource.
Now compare that to having a possibility to replace 20% (or 33% or whatever) of the gold cost of any construction etc. with materials, no matter which kind, where more variety is better than less variety. On micro level you would still have materials and food flowing to cities and goods from cities to the provinces, as well as the provinces trading their surplus materials for what they lack. On macro level you would have currents of surplus materials traveling towards areas that lack them, food included.
I just wonder if additional complexity is really worth the effort.
