I don't think that it would leave keyboard players disadvantaged. They would just have to rely more heavily on tapping to turn slower. I actually find that I perform better using the keyboard, even though I like using the gamepad.
Another thing, this doesn't really display the same spacial mechanics of the original game. In the original, you couldn't really ever stop. You could just burn your engines and move faster. If you stopped burning, you'd carry on that momentum because you're in space. If you turned, you'd be facing in a different direction than your direction of travel. To fix this, you would have to either turn and burn, or burn after turning. Doing so would kind of add velocity to a different direction. You could travel in diagonal arcs even. The only way to slow down would be to flip a 180 and burn in that direction.