There are two components here:
(1) a system to reduce your (non-exploration) speed based on granular but easy to track encumbrance.
(2) a linkage of that to the hp system, representing the drain on your stamina that lugging around 60 pounds of gear underground in a cthonic warzone might be.
The point is to make encumbrance always something you're considering without it being a huge hassle.
I want to make you always be saying things like "I set my pack down while we search."
You can only use (1) if you want. (2) doesn't scale well right now.
You have slots of encumbrance and an speed penalty.
Each unit of speed penalty is -5 feet to your movement.
Normal worn stuff is fine. Heavy/awkward worn stuff and/or heavy armor is +1 penalty.
Normal adventury stuff held in your hands is fine. + penalty if really big / heavy / awkward.
If you've got nothing in your hands, reduce penalty by 1. If no penalty, gain 5 feet to movement.
THINGS IN CONTAINERS
For everything else, it goes in a container.
A container is divided into roughly 5 pound slots.
Bandolier: 1 slot
Pouch: 1 slot
Loop: 1 slot
Backpack: 8 slots
Sack: 6 or 12 slots
You can try to make a container for more slots, but you run the risk of wear/breakage.
After getting your base penalty above, add up all your used slots.
For every 6, -1 speed.
The remainder is a possible additional penalty.
When you need to book it in combat or at the start of an exploration turn, roll a d6. If you roll over, fine. Otherwise, additional penalty this turn/round.
Now, your speed penalty?
4e: That's also how much hp you lose at the end of the exploration turn.
Old School: make a weariness tick mark at the end of each exploration turn in which you suffer an encumbrance penalty. Instead of making a sixth tick, reduce maximum hp = speed penalty and erase the tick marks. Resting for a turn restores maximum hp.
SLOTS OF THINGS
* rope: 4
* sack, small, empty: 1
* sack, large, empty: 2
* torch (3): 1
SCALING BY LEVEL
The hp loss/cap doesn't scale well! I don't really care myself since I'm not advancing hp by level in my current game.
I don't have any ideas here. Maybe I'll update later.
SUMMARY OF PROCEDURE
1. Calculate base speed penalty from armor, things carried awkwardly or unsecured to body, and really heavy things. Does not include normal carried/worn adventury stuff.
2. For every six filled slots, further -1 to speed.
3. Decide this turn if you will set your stuff down or not (i.e., if you'll have to deal with encumbrance). Also decide if you're resting. If you're resting, don't worry about encumbrance this turn.
4. At start of turn, if you don't roll over remaining number of slots (i.e., remainder of total slots / 6), further -1 speed this turn.
5. At end of turn, if playing 4e, lose hp = penalty his turn. Otherwise, make tick marks = penalty this turn. Instead I making a sixth, reduce max hp by 1 and erase tick marks. Resting for a turn restores hp cap to max.