Harrier was designed in uk/us, so that is not really a good example.
But coming to J-11, as long as all key components are made in china there should not be an issue. The main task at the moment would be to remove dependence on Russian engines.
The Harrier is very much an entirely British design which the Americans license built and improved in the guise of their AV8 designation. In a way, it is a good parallel of the Su27 v J11B.
It is also wrong to suggest that no innovation has gone into the J11B. Plenty has, in the form or improved internal structural design that uses more composites and reduced weight as well as subtle external changes that are reported to have lowered the RCS from 15m^2 to 5m^2 without compromising the original airframe design.
The radar and avionics are far superior to the original Russian set and the the engines are likely to have a longer life then the Russian AL31s.
Compared to all these internal innovations, the external design is far easier. But why re-invent the wheel for no good reason? Has any of the Russian 'super flankers' departed much from the original Su27 design other then maybe a few superficial changes like reduced RCS measures and canards?
It can be argued, and many have, that the Russian T50 is like the ultimate evolution of the original Su27 design. But why would China want to follow that road when their own 5th gen design is at such an advanced stage already?