This system may be a possibility. But not in the near future. These are the primary hurdles.
Firstly a ship is a moving target. So you're going to need a maneuverable re entry vehicle on the ballistic missile. Technology only currently possessed by USA, Russia and China.
Secondly these missiles require vast arrays of advanced over the horizon radars. Again something pakistan does not possess.
And most importantly, pakistan has next to zero capability in terms of guidance satellites.
Another major issue is funding. I doubt its possible to develop all of this with the current economic situation.
Remember, I'm not saying this is not possible. With chinese assistance (Especially after the brilliant DF21) Radars can be developed, satellites can be launched. Reentry vehicle tech. cant be shared though.
But to say this tech is easily within reach because of the Ghauri and Shaheen programmes is stupidity.
Cheers and best of luck.