In part, to counter those S-400s. The S-400 is a long-range and hi-level system, which in turn necessitates lots of low level (e.g. SPYDER, MRSAM) coverage to close gaps. Moreover, leaving the S-400 fixed in a place for too long will alert the PAF (and PA) to its location. If there is ever an opening, a large fighter can exploit it by releasing a lot in terms of SOWs (including ARM and ALCMs).
To be fair though, the future of such in land operations will fall upon 5th gen. The other part of a long-range heavy need is being able to provide maritime A2/AD, potentially over SLOCs.
Wouldn't matter unless export credit is available (or in Russia's case, countertrade).
Sir, here is the low down on modern aerial warfare in dense EM environments.
If a radar, any radar, were to be kept turned on continuously, it would get obliterated by ARMs. This is what happened to Iraq, it was the lesson learnt by Yugoslavia. In war time, radars emit radiation in a random pattern that cannot be detected - at least easily. Think how a flesh eating plant snares its prey with honey traps. Its a subtle game of predator and prey.
You need sophisticated ELINT platforms to analyse enemy's signals and guide your aircraft accordingly. You are right, it is about finding gaps. And then taking advantage of gaps through fast action.
But it is wrong to say that EFT would be helpful in this scenario. There are no LO characteristics on the EFT. As opposed to that, the Thunder, because of is small size, is actually a better choice for quick action in dense EM environments.
In any modern air war, you don't send 'heavy strike fighters' 'deep into enemy territory' on day 1. You start by taking down air defences. And it is a very delicate art of subterfuge that involves special forces operatives, stealth helis/drones, ARM and cruise missiles, ELINT aircraft, Wild Weasel fighters such as J-16, F-16, F/A-18E Growler, and stealth aircraft. The F-35 combines wild weasel with stealth. The EFT can be configured with such pods, but its not as if its the best choice on the market for that job. What matters for SEAD missions is the total output power the fighter can generate, the sophistication of the sensors to detect radar waves, LO/Stealth to minimize own signature, and sophistication of offensive beam to jam/spoof the radar. Availability of EMP weapons is also a factor. The point being, this mission can be performed equally well, with or without EFT.
The deadly concern for PAF today, is that Rafale is a true swing role aircraft. It is the closest you can get to buying something like the F-22. You can bet the French have gone to lengths to ensure it has extremely sophisticated equipment for all of the above.
At this point, the first thing we need to be thinking is to safeguard our own airspace. The Syrian tested solution is A-100 AEWACS for long range detection + jamming, and S-400 for air defence. Obviously, you will need other systems to 'fill in the gaps'. But just acquiring them won't be enough. We need a huge investment in developing the doctrine and strategy to wield these platforms. Its a huge learning curve for the airforce, but it is the need of the hour.
Indians will/have deployed 18 SPYDER-MR systems in addition to their existing SHORADs and the medium range Barak being developed by Israel will also enter service soon in significant numbers.
SHORAD is covered by upgraded S-125 Pechora, Akash, Osa & Kvadrat batteries.
What exactly is the 'opening' you are talking about?
The radars are fully operational at times of tension. S-400 gives you the liberty to place the system hundreds of km's from the border. That is much more than the range of any SOW the PAF fields.
In case you are suggesting firing air and ground launched cruise missiles towards the S-400 deployment sites (which are likely airbases), you will need a large no. of platforms (Babur TEL's and Mirages in Pakistan's case) before thinking of anything 'offensive'.
Regarding Pakistan's A2/AD, I believe new corvette's & frigates are more urgently required than something like Typhoon. I would rather suggest the Navy establish an air arm operating AShM equipped JF-17's. SLOC protection is something out of PN/PAF's current & near future capacity.
Or if the PAF requires something for nuclear delivery. You earlier suggested PAF should develop a 'Raad Lite' for the JF-17 with 300kg warhead. Does Pakistan have the capability to produce such a nuclear fission warhead? As per available info, warheads on Nasr, Babur & Raad are bigger.
Read above.