Tactically J-20 would be a game changer however maintenance would very challenging. J-20 would open up doors for western stealth aircraft specially F-35A's. Though this is another topic.
If PAF wants a Bomb Truck then why did PAF decide to modify the A5 Fantan for dogfights. So the argument of JH7's becomes pointless.
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What PAF would like to have is an aircraft design that can be further upgraded for at least 20 more years. This indicates that Project AZM is the first priority hence a Stealth Platform would be ideal. If we look back at what the French Rafale brings to the table is a design that can be further improved to a more stealthy aircraft with far less efforts in time and money. Now on the other hand Boeing has been working on a similar strategy and has developed various solutions for both F-15 and F-18's. Both these aircraft are fraction of the cost of F-35 hence they are still popular among those countries like South Korea, Australia and Canada. Canada would not procure any more aircraft from USA hence they have a problem selecting an ideal aircraft (most likely contender would be EFT).
If PAF plays her cards right then PAF may acquire F-15E in limited numbers and get them upgraded through Boeing to a similar configuration that KSA and Singapore have. Somehow this is not being done by PAF rather PAF wants to procure the big ticket F-35 or J-20.