Do guided-missile submarines already serve as a form of arsenal ship?
Short answerYes; SSGNs are submerged arsenal ships and can serve alongside SSBNs in a mixed strategic-submarine force.
NotesNavies already possess slow, heavily armed arsenal ships in submarine form. The guided-missile submarine, or SSGN, is the submerged version of the concept. A mixed strategic-submarine force could combine SSGNs with ballistic-missile submarines rather than treating every large missile magazine as a surface-ship requirement. Concealment and force allocation offer alternatives to concentrating all strike weapons in a visible hull.