The mule, or pack animal ideas, are probably best.
Backpacks shouldn\'t be for carrying anything over say a short sword, or some gold or whatever, maybe some potions, extra flasks of oil, and food. You may be able to carry an extra shield across your back which was quite common, as shields were cheaper than armour and helped prevent being \'backstabbed\', when you were to poor for a full breatplate, and set of mail.
I think the ultimate system, is Bigby\'s portable hole, inside a bag of holding. And old D&D trick. It would carry infinite items, and weighed nothing.
Pack animals were successfully implemented in Dungeon Siege.
Most of the systems pondered in the threads of this type are Diablo style, and it was sufficient to an extent.
But for a player to be able to carry 4 halbers, is insane. It\'s not so much the weight, as the awkwardness. Which has been brought up.
Different animals, or grades of pack animals could permit carrying more or less, I\'m all for those ideas as well.
Something like a mule, could no carry anywhere near as much as say an oxen, or an elephant.
If horses will be implemented, they can double as both, saddle satches and extra weapon rigging was quite common of battle horses. But they were not so good with extra weight, as it defeated their purpose in battle.