My response to this idea is confused, because on the one hand, lugging anything heavy over your shoulder with a 6-10mm rope would be really painful, but most of the “rope” in game actually comes from seat belts, which would be marginally better than using regular rope.
Eh. The existing weight system would cover half my objections to this, and modeling the shoulder straps like a waterskin, which increases the volume of whatever it contained would cover the rest. I’d say, implement like a tool belt that could hold a single large volume object.