The thing is, if you look at the J-20, its strakes and tailfins aren't entirely necessary once it has TVC. The J-20, in its present design, is likely not going to be as stealthy as other 5th gens, given the combination of the canards, the ventral strakes, and the tailfins. Put another way, if you look at the F-22 or Su-57, the latter two aircraft have 3 separate planes, composed of the main wing, and the tailfins. The J-20, in contrast, has either 4 or 6 separate planes, depending on how you count the ventral strakes and tailfins. By removing the tailfins and ventral strakes, however, you go from 4-6 to only 2 planes, made up of a wing and its opposite canard.
Dunno, one big problem is that this would create a loss of yaw control, cancelled out partially by the existence of canards. There probably would be a need for a quadruple rear aileron, as in the X-36 and the B-2 bomber, but that creates further issues with edge alignment.
