Why nuclear and conventional missiles should stay separate

Should Trident submarines also carry conventional cruise missiles?

No; nuclear and conventional weapons should be kept on distinct platforms to reduce ambiguity and accidental escalation.

Nuclear-armed ballistic-missile submarines should remain distinct from conventional cruise-missile platforms. Mixing both weapon types on one boat creates room for mistaken handling inside the force. An aircraft or launch platform could go into action with the wrong kind of warhead. Keeping nuclear and conventional weapons on clearly separate systems reduces the chance of accidental nuclear employment.