Pakistan has long suffered from the notion that fighters and only swarms of fighters can protect its airspace. It is a lock-on bias that PAF only thinks about one solution to its air defense issues. Some problems are solved using a number of strategies, and the more complex the issue, the more multi-directional approach you need. Something as complex as defense of your airspace requires you to work on multiple fronts.
1. Fighters: Not going to discuss this more because we all kind of understand this, better quality and higher number of fighters with capable pilots improves successful mission rates.
2. SAMs: These are important on a number of levels. The notion that it is changing 70yrs of doctrine means nothing. The doctrine is old and useless, especially in the age of modern strike/stand off weaponry. If anything, the last 2 weeks should show PAF the importance of having SAMs. In the defense against aircraft, they are a support/buffer for your aircraft. They plug holes where no fighters are and protect your fighters in the air (acting as sort of a wingman from the ground. Case in point of plugging holes, the nearest airbase to Balakot is Kamra, which is over 160km away. A jet would need 10min plus to respond to any attack in that sector, let alone over AzK which has no airbase near or in it officially. SAMs scattered throughout AzK or closer to the Indian Border could have turned back the IAF fighters before they even approached Pakistan Proper. It would buy time for PAF fighters to mobilize.
Pakistan needs a multitude of SAMs scattered throughout the country so that they entire nation should be under the veil of a SAM of some type and these should be of various types including high altitude long range SAMs like Hq-9B which will attack at much further distances and force the IAF fighters towards the deck which would essentially (as
@Bilal Khan (Quwa) state), decrease the effective range of IAF stand off weaponry, buying further time to get PAF fighters on station. These need to be backed by a LOMADS like HQ-16 and Spada 2000. Furthermore it needs point defense SAMs (like Hq-10 or even C-RAM from south africa based on Cheetah/Mongoose3) around high value targets like government facilities, power stations, Dams, airports and military bases. The LOMADs and point defense SAMs will enable engagement of fighters closer to the deck so that you have multiple layers and altitudes of defense.
The other benefit that these systems have which fighters cannot provide, is the ability to intercept ballistic and cruise missiles as well as stand off weapons like glide bombs and missiles. Pakistan already has LOMAD HQ-16 and SPADA 2000, but needs to add the long range/high altitude component, ideally with HQ-9B. Additionally i think a system like the C-RAM system based on Cheetah and Mongoose 3 would be especially helpful along the LOC where Rockets, Artillery and Mortars are falling on a near daily basis. Pakistan desperately needs this system to defend its people and really take a bite out of Indian capabilities in that regard.
3. Strike: Yes, offensive strike is an important part of air defense. With PAF having minimal strike capability against India beyond ballistic missiles, it gives IAF carte blanch to dictate the pace of any conflict. For PAF, the ability to push back IAF forces depends on PAF being able to carry out more sorties per aircraft. The IAF can field more fighters, but it needs to have turnover. Given PAF will be the defensive force it should naturally have a shorter turn over. This is by virtue of having to fly a shorter distance. If PAF was able to launch attacks on IAF FOBs, then those aircraft would have to fly further to get home and refuel/reload. That is less sorties that they can fly. That would enable PAF to dicatate the pace of the conflict. The problem is when India takes control of S-400, it will be able to reach deep into Pakistan and knock down PAF fighters from well inside India. So how do you take out both S-400 and FOBs of IAF to ensure that they have a very difficult time establishing air superiority? Cruise missile strikes. But you need to be at a safe distance so IAF stand off weapons cant reach you. Enter the H-6K which can carry 6 cruise missiles. An air launched version of Babur could have a range in excess of 1000km which would enable H-6Ks to sit deep inside Pakistan, where they are protected by AWACs, Fighters, and SAMs, and launch saturation strikes against S-400 positions and FOBs of IAF where 2 H-6K could likely overwhelm a FOB. This would push IAF fighter back further preventing them from having rapid turnover and preventing them from carrying as much weaponry (need more fuel to get into the fray because they fly further so you sacrifice weapons for fuel).