I love that sort of abstract resource management. It's one of my favorite things about games like Burning Wheel, rolling to see if you can afford to buy something, rolling to see if you know the right NPC, rolling to scavenge up some useful item, etc.
Does Donjon have a mechanism for improving the Provisions score? As you probably know, BW lets you improve it by using it. That's the piece that's sort of missing from D&D. Although I suppose we could treat it like a saving throw, and advance it when the character goes up a level. That'd be darn interesting.
The categories would really make the difference here. It'd be easy enough to have really generic saves like Adventuring Gear, Hand Weapon, Ammunition. But it'd be cooler to have categories like Tunnelcraft, Lore, Potions, Boot Knife, Last Arrow, Bits & Bobs, Camp Gear, etc.
Dwarves and Elves would have good saves for Tunnelcraft & Lore, respectively. Potions are the domain of the M-U, and both Fighters and Thieves would have high chances for a Boot Knife (or other backup weapon) or another arrow. Everyone would be decent at Bits & Bobs, but especially Halfings, and Retainers would excel at Camp Gear (including torches and oil).
(I admit it, I'm a closet indie gamer!)