I don't think new currency systems are really needed. Just make camp supplies drop from combat and quests, and reduce the amount you find in random containers.
That wouldn't be the worst thing, but you could still hoard lots of supplies early on and then do multiple rests later without doing anything in between, which doesn't make much roleplaying sense, and if you really think about it, the food already is a currency. Basically, drastically lowering the amount of food and placing it more strategically would be functionally similar to my proposal, without the added benefit of preventing hoarding, and being able to use the resting system as a difficulty scaling tool.
