More composite materials instead of alluminium body. Makes it stealthy and light weight.
Chinese IRST. ( its very good for surprises)
New Landing gear to lift it off the ground its too low in my opnion when on runway. Also that enables more room for a cruise missile or a drop tank there.
Onboard oxygen generation system (may be, not as important)
Full Fly by Wire system.
Side stick instead of russian style mid stick.
Deployable parachute if engine or a component fails.. To decrease speed and tailspin mid air (safety)
1200 modules chinese AESA radar with atleast 225 km track/lock ability. Possibly both sides coverage too left and right of aircraft (chinese have the radar with these capabilities )
True fire and forget 170 km ranged air to air missle.
Chinese have Air to air missiles of 350 km range already but they are very long and huge . we need nerfed down Sd-10C perhaps.
Avonics that enable re-routing a cruise missle or air to air missiles fired by friendly jf 17 aircraft, chinese are experimenting with this.
Engine improvement to have thrust of 100 KN atleast.
Helmet mounted Display HMD, and a MFD glass hud from j-20.
Total integration with Beidu settalite Navigation system for navigation and weapon grade track/guidance. Its total blackout for enemy and extremely hard to jam, hack.
Lastly perhaps a dedicated EW jammer and disrupter variant that could possibly house reconicense equipment.