Nuclear submarines being able to carry nukes or conventional missiles

Allow submarines to carry both nukes and/or conventional missiles. Just like in real life submarines are essential part of nuclear deterrence hence adding this capability to Humankind will transform "Contemporary era"  as a whole adding more intricacy and tactics into late game. In addition if detected(by specialized ships or just by ship adjacent to the path of the submarine) in adjacent waters a nuclear submarine could pop up as grievance as well