Thank you for your reply. This is what I was thinking. So, essentially, CJCSC's role is been given to COAS, which is not unprecedented since Prime Minister Nawaz Sharif had already done that with Musharraf back in 1998.
As long as there's no interference with the operational aspects of the services, which I believe no Air Chief would agree to, even Mushaf Ali Mir, been handpicked by Musharraf after superseding top leadership of PAF never compromised on PAF's operational requirements.
I do think a CDF position where all services could get a chance to lead would have been better but seeing ground realities, I guess this isn't bad afterall. As long as it's implemented properly, and not left for ceremony like JCSC office was.
Yes, BUT with a major change.
CJCSC was a quasi-ceremonial, strategic planning post. It has no operational command over anything material. The respective chiefs held all the control over how the strategy was to be implemented by their forces.
The CDF fundamentally changes it. It reminds me of a few lines from the movie "Remember the Titans" in the following dialogue:
"Coach Boone: Let's talk football.
Assistant Coach Yoast: I run the defense--
Coach Boone: As a part of my team strategy. Now, I have never seen an assistant coach's name in the newspaper for losing a game." 
Meaning the overall conduct and responsibility for military operations will rest with the CDF. This was not the case with CJCSC. It will be the former's strategy and operational planning that will be questioned if something were to happen.
Thus the relationship with the CDF role and the services chiefs. The CDF is the leader of the higher defense organization (HDO). He holds not only the final call on the overall defense strategy, but also has the ground component under his command to implement it on the land. The other services chiefs are part of his team and have their distinct commands to run but in full coordination and alignment with the CDF. I also think, under the new structure, the VCoAS will become a more prominent role within the Army.
This by the way is no different than the US Joint Chiefs and the UK CDS. There is noise about doing this because of the current political overlay with FM Munir. Minus him and the politics around him and this call is a sound one. I also do not see the CDF telling the CNS or CAS to appoint someone to a post within their respective services because it is strictly their purview. However, the higher promotions within the services may become a more centralized process as the senior officers would be expected to operate in the "joint" capacity far more.
The other benefit will come by way of a more optimized spend on the military procurement. All procurements will have to align to joint plans. They will be vetted and approved with greater transparency across the HDO so the acquisitions are more effective for combined operations.
Over time, it is possible that other services chiefs will be able to land the post of CDF, however it remains to be seen. I think it is alright to get the CDF centric HDO off the ground with an army officer leading it for now.
Last point, on your question about whether this will help avoid future Kargils, yes, because at least conceptually, the inner staff of the CDF, who is also the CoAS, will include the 2 other Service Chiefs. Second, post 2019, 2025 conflicts, a Kargil like operation cannot happen without it becoming a full-scale war. This is understood on both sides now.
but there're more nuances to where the blame shall finally rest and if that event can be used as good example against a unified command structure. I'll wait for others to present their side first.
and if the argument is that things have now changed within PAF then the argument applies to CDF too. Also, if the argument is why only Army General for CDF, then the same argument applies to why only GD(P) and mostly Sargodhian for CAS.
