J-16 is developed from J-11 which is itself a licensed copy of Soviet/Russian SU-27. Russia will not allow China to export these jets to a 3rd Party. Same is the case with J-15, it is an unauthorised copy of the SU-33 so here too it is unlikely that China will be able to export J-15s to Pakistan because Russia will most probably block the sale.
So buying Chinese Flankers which are they themselves copies/licensed copies of Russian Flankers is totally out of the question.
Twin Engine Fighters like SU-30/J-16/MiG-35 etc are more complex to maintain, more expensive to Procure etc.
You are better off using JF-17s only. For Anti ship role, JF 17 can Reportedly carry the following :
- C-601 — (Anti-ship missile)
- C-705KD — (Anti-ship missile)
- C-802AK — (Supersonic anti-ship missile)
- CM-400AKG - (Supersonic anti-ship missile)
- HD-1A — (Supersonic anti-ship/land-attack cruise missile)
SOURCE : Wikipedia.
So JF-17 is good enough for Anti shiping role for you. China also has JH-7. Maybe they can give you that.