Actual studies show there are 125 to 150 police suicides per year, at a rate of 14 - 17/100,000 (the public is 11/100,000 and the Army in 2009 was 20/100,000).
I don't understand the logic of this debate. A malcontent in the front seat has plenty of opportunity to cause harm and perhaps will not wait for a toilet break. If you are content with two crew up front most of the time, introducing a temporary stand in only increases risk. Only real mitigation would be to return to 3 on the FD, all screened as now.