Brainstorming Encumbrance. If of interest we can coordinate this approach with other mechanics later.
Armor Encumbrance. Encumbrance that is caused by armor is counted separately from the loads from other items. Armor is more about how much it gets in the way of Athletics stunts, rather than how much it actually weighs or what its size is.
Most items are Negligible. Unless one is Tiny, Negligible items dont count toward ones Encumbrance. Nonnegligible items qualify as a Size
A creature can Carry 7 items whose Size is one smaller. The eighth such item counts as the same Size as the carrier in total. An items that is two Sizes smaller than the carrier counts as Negligible if it is worn securely in reasonable a location or packed inside an other item. A Tiny creature can only carry 7 Negligible items. An item or a group of 8 items that is the same Size as or more than the carrier requires Weightlifting skill checks. Two or more characters can split a load if there is a reasonable way to securely carry the load together.
Negligible
• Dagger
• typical garment, such as shirt, pants, skirt, socks, belt, boots, etcetera
• wallet or securely belted moneypouch
• jewelry or similar adornment
• small vial (about the size of a testtube)
Tiny
• Shortsword
• Backpack
• Satchel, or purse hanging from strap
• Light Cloak, cape, mantle, etcetera
• Heavy Robe, or other fullbody winter clothing
• Pint Mug
Small
• Longsword
• Camper Backpack
• Heavy Cloak
• Coffer, Money Box (empty)
Medium
• Greatsword, or other Heavy Weapon, such as a polearm
• Carrying an Unconscious teammate who is Medium
Note. A Medium creature normally requires a Strength Weightlifting check to Carry a Heavy Weapon thus wield it without Disadvantage. A Small creature whose Strength Weightlifting check Carries a Heavy Weapon, can wield it normally.
SIZE-WEIGHT
The Size-Weight Table is a variant rule at the discretion of the DM. A DM might decide an accumulation of Negligible items is becoming unreasonable. Or a DM might wish to assign a Size to an unusual item, and knowing the weight might help decide. Each Size is a weight that is about 5 pounds times a multiple of 8. A DM should avoid precise calculations and rely on reason when near the cusp between Sizes. Use the Size categories as ballpark approximations. The Size-Weight Table for items should be in the Players Handbook so players are aware of it, but only the DM would be the one to invoke it.
GARGANTUAN: over 20,000 pounds
HUGE: upto roughly 20,000 pounds (20,480)
LARGE: upto roughly 2,500 pounds (2,560)
MEDIUM: upto roughly 300 pounds (320)
SMALL: upto roughly 40 pounds
TINY: upto roughly 5 pounds
NEGLIGIBLE: upto roughly ½ pound (0.625)
Note: 50 gold pieces weighs 1 pound. These are small thin coins. Compare a US $0.25 "quarter" weighs 0.2 ounces, a fifth of an ounce. Thus a gold piece is a bit less than two quarters. If familiar with the uncommon US 50 cent coin (also called the half-dollar coin), this is about the size and weight of a D&D gold piece.
GARGANTUAN: over a 1,000,000 gp
HUGE: upto roughly 1,000,000 gp
LARGE: upto roughly 128,000 gp
MEDIUM: upto roughly 16,000 gp
SMALL: upto roughly 2000 gp
TINY: upto roughly 250 gp
NEGLIGIBLE: upto about 30 gp
Notice most characters are porting around an amount of gold equivalent to Small Size.
So the above is the brainstorm. The gp coins come in ballparks without precise calculation. Negligible items normally dont count toward Encumbrance. The limit of seven one-Size-lower items are generous enough before invoking Weightlifting skill checks. Armor counts separately toward its own Armor Encumbrance.