I have noticed while playing that fuel doesn't last very long, especially when cooking. It takes an absurd amount (around 8 firewood) per meal in a cooking pot. This is even worse when you try to cook a stack of an item over a campfire. You can be more efficient with an oven but cant make meals inside one. I would vouch for the addition of longer lasting fuel sources you can with relative ease make for the sake of bulk cooking or other long processes. Or at least a system similar to the forge. Its very fuel efficient and get its job done at a relatively fast pace, so much so you can probs get 4 bars into finished projects with 1 charcoal. I would love to see a similar system be added to campfires, or at least have longer lasting embers, so that it stays hotter for much longer.
There are some mods out there that do adress this issue like Fuel briquettes but it would be nice to see it added to the base game.