MiG-29
Banned Idiot
you can not modify the Su-27 much because the aircraft has a limit in modification, even the Su-34, Su-33KUB, Su-33, Su-30MKI and Su-35S are changing few elements and moslty the crew arragment and canopy configuration.^ Yeah that didn't say anymore than what I did..
The J-11 can not do more.
The current Su-35S has just a lightly higher composition of lighter materials, some RAM and a modified AL-31 aka 117S, but most of the jet is a Su-27B, in fact the Su-35S is closer to the original aerodynamic configuration of the T-10S than the T-10M or Su-10IB aka Su-35 and Su-34.