IMO pakistan dont have enough funds for nuclear subs at this point..... they will probably ask china to lease them a few improved 091 SSN for study.......
The more recent Yuan class diesel-electric submarine would be technologically superior to the 091 SSN. If I was Pakistan's Navy I would mix it up with Agosta 90B and the Scorpions which was reported to being offered from France and the Yuan class.
Your right. The Navy can't afford Nuclear subs but conventional would be best to support their waters. Its not in Pakistans interest to wander deep into the Indian Ocean where India is best in fighting in Blue Water.