If you raise your sword in alignment with the attacker and enter, like a mirror image, like ikkyo with the sword, and enter irimi and tenkan then you will find yourself facing the same way as the attacker but your sword is now ready to cut down his back or even arms if you wish or shoulder take your pick depending how deep your irimi was.
I know exactly what you mean as we have all done that to death. But is it a sensible way to train? I agree with Ellis. Train more irimi
to go right thru him. The enigma is, that by practicing more irimi
you will actually find your self getting better at the movement you described above, but then, having practiced irimi
more, you will find yourself doing less of that technique explained above because you will have less need for it.