This is the most relevant threat as far as Pakistan's key strategic issues are concerned. Congratulations Sir MK.
Now coming to the debate. I think the most basic question which need to be answered is about the doctrine of PN.
What is the current and future doctrine of PN?
What is the strategic role of PN in Pakistan's overall active-defense mil strategy?
Is PN getting adequate funds for this national mil strategy in context of fluid nature of regional geopolitics?
Is it lack of resources or lack of vision and mismanagement of priorities which has led PN in its current predicament?
The answers to these questions are essential, if not critical, in order to move this debate forward towards its logical conclusion.
Unfortunately, it is evident that Pakistan Navy's doctrine is still "Coastal Defense" with very very limited Sea Denial capabilities. This doctrinal approach leaves very less space for any aggressive thinking as far as operational planning of current PN fleet is concerned. But, are the Coastal Defense capabilities of PN are adequate for modern times when the threats is being posed by modern guided missile destroyers and frigates and of course by aircraft from aircraft carriers, instead of small sized warships based on 1950s or 1960s technology? IMHO, PN still lacks on couple of crucial aspects here. ( Number of surfaced and sub-surfaced vessels, credible SAM capabilities).
Security and Threat Matrix: Indian Guided Missile Destroyers and Balance of Maritime Power in Arabian Sea
Purchase of 8 SSK will only enable PN to perform this role of coastal defense adequately. It is important to understand here that not all the submarines would be deployed simultaneously. So having a larger sub force makes complete sense. But here comes the point when the question raised by Mastan Khan in his first post of this threat needs to be answered.
In my opinion, what MK proposed is more logical and practical and would be more beneficial for PN in the long run.
We know Chinese have been making big strides in defense R&D for last two to three decades. What China is producing today is based on 1990's era technologies as far as Naval vessels are concerned. But by the end of this decade, they will bring in production what they researched in last decade. Now, if we today decide to buy 8 subs based on 1990's tech we will complete the delivers around 2023-24 timeline. By then, Chinese will be producing more advanced subs. So, why not split the deal for 4 existing platforms (S-20) and 4 future projects (it may be a JV) and meanwhile focus on strengthening Naval Aviation Wing of PN. I am not putting surface vessel in priority #2 here because they are a)- Expensive b)-takes much more time then inducting Aircrafts (MPA, Multirole Strike platforms etc.)
Naval aviation is more relevant and demands more immediate attention of strategic planners who wants to strengthen currently non-existent sea-denial capability of PN. Naval aviation will do it along with subs. This role can not be performed by either subs or aircraft alone!
Back in 2012, I did write a research paper on "Eurasian geopolitics and Emerging Trends of Naval Aviation in Indian Ocean". It was published by National Defense University Islamabad. It can be downloaded from below link if someone wants to know the details of my argument in favor of Naval Aviation.
Eurasian Geopolitics and Emerging Trends of Naval Aviation in Indian Ocean | Shahzad M Roomi - Academia.edu
But does that means surface vessels are to be ignored? Not at all. But my view is before choosing the platform, we must come up with the answers of questions which I raised earlier in this post. Unfortunately, in our political elite and military leadership there are very few minds which are capable of addressing complex issues in defense doctrine of the country and its linkage to the statecraft like foreign policy and military diplomacy.
Americans know what role Aircraft carriers play in their foreign policy of maintaining leadership position in the world, Indians are producing larger destroyers and frigates along with expansion of their air wing because political goal is clear; "to make Indian Ocean, India's ocean" ... So how critical Arabian Sea is for Pakistan? What role we want to play in this sea? How far we are willing to go for the realization of this goal? These need to be answered. The answer will determine what kind of surface fleet we will be needing. Fast Missile Boats and Corvettes or Larger Frigates and guided missile Destroyers?
To me right now, Pakistan's political and military leadership must revisit geopolitics of Indian Ocean and reassess the requirements of PN's role in Arabian Sea. PN must able to project credible maritime fire power instead of continuing to follow Coastal defense doctrine. The imbalance between IN and PN has gone horribly wrong and needs to be restored without bringing N-word in this debate. So, Yes we do need heavier surface vessels along with more subs then what we are negotiation right now. But since the time is linear in nature, first we will have to ensure we do have credible coastal defense and for that PN must concentrate on larger fleet of heavy FACs and Corvettes armed with latest sensors and long range anti-ship missiles. This way PN will able to maintain its presence all along coastline. But if the political goal in context of Arabian Sea changes, this surface fleet plan would also move towards Frigates and Destroyers.
Second Strike Capability: I think Pakistan will have to bring maritime balance of power ( by it I mean the capability through conventional means which can ensure stability in Arabian Sea) without lower the nuclear threshold any further. Due to Indian Cold Start Doctrine (CSD) it has been lowered already. From pure political and diplomatic view point lowering the N-threshold is not a wise strategy. Second Strike capability is critical to ensure nuclear triad but PN must not devise all operational plans based on this capability. N-Strike is always a political decision. PN must develop itself as a potent force in conventional means.
Budget: A lot has been said here about lack of financial resources. Well, to me ... finances is not the problem. It is the political will to transform PN from a small defense fleet into a ruthless force. The N-tale of Pakistan is best example in this regard. It was a problem only as long as political vision was not there. Once Bhutto announced that we will have it at any cost, it started to become reality which eventually manifested in May 1998. So, stop looking at financial figures and start focusing on political will of Islamabad about PN, Arabian Sea etc.