As a smith in one life and a miner in another, I understand some of the problems and benefits of each.
As a smith, I was always in need of ores to make weapons and such and I predict that this life will be no different. That being said, the miner must be allowed to carry at many ores as his or her strenght will allow. To limit everyone at the same amount gives no reason to build up their strenght.
If there are monsters in the mining vicinity who attack and distrub the miner, he or she will have to also carry armour and weapons to defend with. This will add to the weight and will limit ore capactity also.
Speed should also be affected by the weight and strenght of the individual.
Of course, this is just my opinion.
