I’d suggest trying the resource system from Alien. I’ve changed my home FbL game to this. Basically you count resources as units 1-4 as a normal item, 5-8 is heavy, etc. Then when you test the resource you roll that number of d6’s. You lose a unit for every 1 rolled.I also want to increase the logistical planning required in adventuring.
I think having all resource dice just take up a single encumbrance slot is too generous, especially for water. Have you ever tried to carry water? It's extremely heavy, and as the RAW read, an adventurer could potentially be carrying many days or weeks worth of water for a single encumbrance. IRL it's hard to actually carry enough water for a whole day, never mind several days or even a week.
My solo player so far has had no problems in making her d12 of water last. The drawback of the resource dice system is that there's no telling how long a die might last, and a d12 of supply could last for weeks. She has now acquired Maligarn, which drains resources from you (forcing you to make 2 rolls instead of 1).
I was thinking of something like this: For food, torches and arrows: D12, D10 = Heavy, D8, D6 = Normal. For water, each die takes up a slot. This might be too harsh, but the player does have a horse.
I'm also considering allowing D4 resources, which would be Light, and the equivalent of ½ rations - you would still deplete after rolling a D6, but you could deliberately pack a D4 to travel very light.
Additionally, have any sort of strenuous activity (hiking in the heat, forced march, combat, etc.) cause additional water checks. The effective water supply will be less while keeping the actual rules for tracking it just as easy.