Won't it all end up just levelling out, if you have 100% food you just trade for the others?
In theory, but regardless of what your workers are digging for.., they all need feeding when a regional harvest is activated.
This is one of my regions and you can see the deficit between grain yield and usage. The region gets more grain than it uses, but many of those plots are Jungles which right now, are grain farms.
When 1.75 comes in, they will switched to log cabins, and so that deficit will then be in the negative. The are gathering wood, but still need feeding.
This is why I feel the 4 food types of land will become more valuable than the others. Everyone will gain wood/stone/ore, but they will also gain a negative deficit.