I think it'll be real tricky to balance right, especially with so much random chance(not necessarily subjectivity; this is meant to make a story). A single die is extremely random, since every outcome has exactly the same chance of happening. And all you need is one bad harvest...if it was just that it might be annoying but it would probably be fine. But when you add in the real-time element, which necessitates being as active as possible for when you update/respond, it becomes a very tricky thing for everyone to navigate. If it isn't handled well by both player and GM, it will become little more than 'continue trying to get food' and 'numerical response'. Where, really, if food is hard to come by, usually a change in methods, or location, or whatever is required. Which might or might not be reflected in subsequent dice rolls. How much you want to dice rolls to decide, too, might play a part; hunting is certainly hit or miss, most of the time, with element of danger or bounty, but farming is usually fairly steady, which is why we switched to it. A 15 versus a 5 probably won't be as large of a difference, proportionally (the extremes are still the extremes, even if 5% chance feels a bit high for a blight to come through). And then, of course, there's the bit where people can usually live off of less than the optimum amount of food, but don't like it, when there's lots of food it usually gets eaten (or stored, if they're smart), and the people are a bit stronger or whatever...
It might be better abstracted, but...I dunno. Abstraction can be tricky too.