The big difference between ground and "common" or "neutral" is the voltage drop that is developed on the neutral wire due to the fact that it has the same current flow as the line conductor (What goes out must return) (Load current x DC resistance of neutral conductor between receptacle and breaker box= Voltage difference between neutral and ground at the receptacle). Normally the voltage drop is neglible except in long circuit runs with higher current loads. The neutral and ground wires are normally connected together (bonded) at the breaker box. I totally agree that the fuse definitely needs to be in the "hot" or "line" or "mains" line to perform a safety function.