Yeah, fair call. I think establishing it's a secondary advantage and allowing him to score off the woodwork as well would make more sense than having him being able to touch it one way and not the other. I normally side with attacking players so I don't mind your rule change at all.
I think I still just edge towards the idea that the punishment for the foul is the penalty and maybe yellow / red card; and that once the penalty is missed the advantage is over and it should be equal opportunity for both sides to get to the rebound.
But I think either of our suggestions are slightly better than the current system.