KAAN fighters powered by the WS-10B used on the PAF’s J-10CE could mean a certain level of commonality. If the PAF eventually fields around 96 J-10CE And about 54 KAAN Fighters it would mean over 200 engines in active use. The PAF could try to get domestic ToT (along side possible local production of the WS-13E) to support its fighters. For the Turks, it would mean the KAAN would be available earlier for export, as a non-western engine variant would be avialable.
How would the KAAN fit in the mix? Probably optimized for the A2A role, whereas the J-31 could be more multi role.