Grid-based encumbrance

I've been rather consumed lately with revising Engines & Empires (yes, a true second edition is now officially forthcoming—and as a standalone game rather than setting for someone else's), and one of the first snags I hit was encumbrance.  I used Delta's stone-based encumbrance in the original publication; since then, I've found that most players just prefer to count pounds.  But there's something so unsatisfying about a "bean-counting" encumbrance system: players scrimp and twist and cajole and wheedle and do everything they can to stay under that first 40 lb. "light encumbrance" threshold… which means that you wind up having a bunch of players who are all running around with exactly 39½ pounds of gear (most of the time; treasure-hoards and bags of holding do alter this equation from time to time).

Most OSR-types readily glow about Raggi's LotFP encumbrance system, but that's actually too abstract for me.  Something about slot-based encumbrance really rubs me the wrong way.  There's probably no rational cause for that; but for whatever deep-seated emotional reason, I just can't grok it.

Expand those slots into two dimensions, though, and now we're looking at something interesting.  Imagine a character inventory sheet that looked something like this:

It consists of two main elements: an 8×8 grid divided in four smaller 4×4 quadrants; and two expanded lists keyed off a pair of squares in the bottom-left grid.

Here's how the system would work.

Normally in D&D, every 40 lbs. (or 400 cn if you prefer) carried is an encumbrance threshold that drops your character's speed by 30' (10').  But what if instead tracking weight in pounds or coin or stone, we instead tracked an abstract representation of the item's weight and bulk?  If we assume that each quadrant of that grid up there represents 40 pounds' worth of inventory space, then that means that four squares represents 10 lbs (about the weight of a greatsword or a suit of leather armor), two squares represents 5 lbs (a hand-weapon or a shield), and a single square is 2½ pounds or 1 kilogram (a full quiver of arrows or box of bullets, a single scroll, a few potions, two or three days' rations, 120 coins assuming coins weigh ⅓ of an ounce as per 3rd edition).

From that, it follows that instead of an encumbrance value representing its weight, every item has a bulk inventory space (à la Diablo), and you can fit items into your grid however you think you can manage, Tetris-style.  But, and here's the rub, you start out by placing items in the bottom left quadrant (as if the bottom-left corner were the "origin" of a Cartesian plane), and you're only unencumbered so long as three of the big 4×4 quadrants are completely empty.  If anything "leaks over" into one of the other quadrants, you're lightly encumbered and your speed drops from 120' to 90'.

Common item dimensions would be as follows:
Dagger, Scroll … 1×1
Broadsword, Shield … 1×2
Blunderbuss … 1×3
Greatsword, Musket … 1×4
Small Spell-book … 1×1
Big Heavy Tome … 2×2
Leather Armor … 2×2
Chain Mail … 2×3
Plate and Mail … 2×4
Full Suit Armor … 2×5 (can't wear this without being at least lightly encumbered, since it won't fit in one quadrant)

…With the usual addendum that small items "stack" or "bundle"—20 pieces of ammunition in a square, 100 coins, 6 grenades or potions, 3 days' rations, and so forth.

That brings us to the bottom of the sheet: two boxes are provided with roughly twenty slots for very small items of mostly negligible weight and bulk (worn cloaks and rings, holy symbols, little trinkets that characters tend to pick up along the way—Tolkien would've called them "mathoms" and I rather like that enough that I'll probably use that very term).  Twenty such ultra-light items fill one square on the grid, but for the most part they can be ignored while a character doesn't have too many of them.

A character's actual encumbrance level, as mentioned above, is determined by the number of completely empty quadrants on the grid:

Empty quadrants … Encumbrance (Speed)
3 or 4 … Lightly encumbered (120')
2 … moderately encumbered (90')
1 … heavily encumbered (60')
0 … severely encumbered (30')
less than 0 … over-encumbered

Thoughts & comments?