I actually doubted the effect that the flexible edge piece have on improving corner cutting, but after seeing the corner pieces, I realized that this design would actually eliminate reverse-cutting lockups completely.
The only source of lock-ups when attempting a reverse corner-cutting is the outside cubies catching on each other; edge-to-edge and center-to-corner.
But for the interior section, it makes no difference to them whether you are doing a foward or reverse cutting; they "open up" and glide over each other either way.
What this means is that, if you eliminate the only factor causing the locks (the outside cubies "pushing" against each other in reverse-cutting), the cube will tolerate reverse misallignments even at extreme angles.
In addition, the profile of the corner piece (I'll explain how that works later, it's have something to do with the center piece) combined with the flexible edge cubie will allow all angles of foward-cutting to be almost indifferent from each other (meaning that it takes approximately the same amount of force to cut 1/2 cubie as to cut 1 cubie) except for minor difference due to the spring's nature (F=kx).
This concept, if refined and cleverly engineered, will effectively eliminate any lock-ups possible.