A proposed ballot measure for an independent Oakland police commission stoked a fight at City Hall Tuesday, when two City Council members challenged Mayor Libby Schaaf’s right to appoint three of the commission’s seven members. Proposed by Councilmen Dan Kalb and Noel Gallo, the measure initially had broad support from the City Council, whose members say the city’s police department needs stronger oversight in light of a recent string of off-duty disciplinary cases. The two councilwomen agreed with several activists who spoke at the meeting, arguing that the commission could not be truly independent — or insulated from the Oakland Police Officers’ Association — if any of its members owed his or her position to a government official. Though the commission would have similar duties it would be more powerful, entrusted to form a Community Police Review Agency to probe misconduct complaints, and authorized to fire the chief for cause, if five of its members vote to do so.