Is there really a 30 mm fun being developed for the J-20? Which could then find its way on to the J-35?
Placement could be on top for the J-20, and in the wing for J-35, similar to how it is on the Rafale with its 30 mm cannon.
I know the philosophy for these planes is shoot and scoot but stealth may not allow that and having a gun (which I know some consider a dead weight) may seem useless, but it could still be necessary.
With increase thrust in future engines, WS-15 and WS-19, respectfully, the two planes could add 2d thrust and become very capable dog fighters, not by choice but if they find themselves in such situation.