Hmmmmm, Im not sure...I have two reservations about this........
Perhaps...
But I think one advantage of this is you don't have to move your head to check your alignments. You might have to move your eyes, but that's not too bad. I actualy think you can probably just do it with your peripheral vision...
As to parallax and that kind of stuff, I don't really see it being an issue. Imagine a flat horizontal surface - like a table top - now imagine bringing your eyes in line with that surface, it appears as a virtually 2-d line. Now imagine a club moving on it - where's the perspective problem? This is what's happen when your club and hands are on the selected plane which you've set up with the mirror. I'm not sure that there can be perspective problems in 2-d!
As I said before, if you swung in the plane of your eyes to the ball, the club and your hands would appear to go straight back and through.