So if the FO calls "Five Hundred Go Around" the SOP is that the Captain will execute a Go Around.
The captain is in charge of the flight and he decides whether or not a go-around is warranted - not the first officer. Your company SOP needs to be reviewed in terms of the Human Factors issues involved. Quite often a nervous nellie or inexperienced first officer will start yelling for a go-around when it is unwarranted. This is often seen in the simulator when a first officer is flying and decides he is going to execute a go-around when it is clear the approach is well within tolerances.
While 500 feet is standard with many operators as a decision point in terms of a stabilised approach, there are other pertinent factors to be considered. It is as bad empowering the first officer to initiate an abort during his take off rather than the captain making that vital decision and subsequent action to reject