Developer Joseph Fallon is showing the city today his plans for a 15-story mix of retail and commercial space right on Boston Harbor, adjacent to the new Fed courthouse on Fan Pier. The idea is for retails and shops to occupy the bottom floors, and floors two to seven (that’s six floors) to be laboratory space. Office space is for the upper floors. Does the city want a towering laboratory on the harbor? Would a future condo or rental development want to be sited next to that? We’ll see.