Doesn't quite work, since the opponent can chose the centre square which leaves you with a free move, but whatever master square you place your free move in, can no longer be used to force him back into the same master square.
The opponent can't choose the center square because you've already filled them all in the initial phase of the gambit.
"Instead of filling in the center square on the last board..."
Why not? All the other squares are empty except for their centers. You can put your opponent wherever you want.
I don't think so. At Orwin -1, picking a non-center move forces O to one of 6 perimeter boards, none of which have that corresponding perimeter position filled. This cedes initiative to O.