This isn’t exactly for FotF, but the context is very similar and wanted to get feedback or any potential mechanical issues pointed out. How does this sound? [bracketed parts are things I’m considering]
Supply is a stat that represents the entire party’s mundane supplies including rations, fuel for light, ammunition, medicinal items, and the condition of shelter and comfort items like tents and bedrolls [as well as your packs and treasure sacks].
Supply is similar to an Ability Score, ranging from 0-18, and translates to a Modifier just like an Ability. [It starts at 15 for a group of 1-2, 17 for 3-5, and 18 for 6 or more, including hirelings and pack animals].
Make a roll plus Supply when a meal, light, ammo, or healing is needed.
Complications and Consequences are determined by the GM, but might include decreasing the Supply score by some amount, time taken while cooking or repairing something, a restless night from spoiled rations or degradation of shelter, or completely running out of one of the types of resources.
[You can always decrease the Supply score by 1 to add a +1 to the roll.]