Funny just how much you derailed from your initial argument of "can Pakistan afford the same"Seems like you finally accepted the fact that Pakistan doesn't have to get pay (or ripped off rather) the same way Indians do.
Secondly, go ahead with giving away your sole Nuclear Sub to some arch rival of China, oh wait, it's not even yet commissioned!And...even if India is delirious enough to give away its nuclear sub, which "Arch rival" of China would DARE to accept it? Japan? Well then that would be a serious breach of its post-WWII treaty and making you guys as much a "terrorist state" as Japan. Vietnam? You can then be sure all of its ports would be wiped long before your sub makes it there. Not to mention it would also be a breech of non-proliferation of nuclear arms to a non-nuclear state, making India into a "terrorist state" again.
The sole purpose of a Chinese leased SSBN would be to give Pakistan a more robust/comprehensive 2nd strike capability, and would/should only be done so after India has developed its sea-borne 2nd strike capability to ensure regional stability, much like the same way when Pakistan came up with its nuclear deterrence back in the 90s soon after the Indians gained such capability.
China does not have the same expertise Russia has with respect to nuclear powered submarines. China is not in a position to offer a submarine anytime in the near future.
Why would Pakistan need a second strike capability ? Your land based nukes seem to deter India. In fact China herself does not have a naval 2nd strike capability against America or Russia. India is getting it to deter China not Pakistan.
