A few thought. First, the system might not be simpler but it is hands off. Lords do not need to do anything. It happens in the background. Second, excess food does not need to be stored centrally. It is controlled by the banker but it can be distributed and stored wherever. Regarding distribution of suffering, I thought it might be possible for the Banker to be able to set a predefined action to take in the case of a shortage. Something like : "Distribute Food Equally", "Feed Cities first" , "Feed Rurals First" or "Set Manual Distribution Order" and allow the banker to granularly give all regions a priority and have food distributed in the order specified. Distribution of excess food can be handled in a similar way.
Looting happens like normal. If you enter a region that would usually produce 100 food and loot it like mad it does not produce as much food and the realm has to deal with the loss. With that in mind I would have each region produce X gold and X food. The increase in gold received by the rurals should be based on the amount of food produced. So If I usually produce X food but only manage to produce half as much due to looting I only get X/2 gold from foot and whatever I should from direct gold production.
Like I said, the idea is to abstract food/gold/trade so that it is largely hands off. As a region lord it is primarily my job to keep the region producing at high levels. Buying, selling and storing food becomes a thing that just happens.