I've grown a love/hate relationship to the game's overworld supply mechanics.
As I mentioned before, tools just won't arrive at resource camps and the camps shut down waiting for them. But there's also starving armies sitting in provinces that actually do have the surplus production (and warehouse) to supply them, but still starving to death, because the game's quirks make it arrive too late.
Now, as such, it's not necessarily a bad game mechanic. Sometimes logistics fail. The lesser bugs could be a feature (even tho tools not arriving at a res camp forever should be fixed). What makes it frustrating and silly is it puts logistics completely out of your control. Silly, because as a despot you ought to have a little more control over affairs than that.
So, my "solution": the supply convoy. It's a unit that has a supply storage much like a trade unit implicitly has, but whose movement you control by command just like your military units. You can order it to deliver and then you can choose the resource camp or settlement or any unit of yours in the same tile. You can then transfer the goods. Or just supply the unit for that amount of resources. You could perhaps even do that in a different province, even in one not controlled by your tribe.
What makes this a nice mechanic imho is, if you invest the time and resources, you get to decide exactly how and when your people get supplied. Of course this becomes redundant if the implicit transport handled by the current trade and supply system becomes bugless and instantaneous, except you still might wanna send supplies into enemy territory (at the risk of the convoy being killed).