The goal line is the focus of scoring and the goal post assembly should reside there as it does for every code of football (association, rugby union, rugby league, Aussie, Gaelic) save one (ok, two if you consider arena football).
Our end zone is 20 yards deep. This would mean teams would have to scrimmage into the red zone before attempting anything short of a 47 yard field goal! A convert would be a 32 yard attempt. Our rouge rule as it stands means every field goal attempt that has the distance and misses will be an automatic rouge giving credence to the CFL haters who say you get a point for a missed field goal.
Goal posts on the dead-ball-line in the Canadian football have too many implications for other aspects of the game. The change worked and still works in the American football because their goal area is only 10 yards deep thus it does not drastically change the dynamics of field position. They also have no rouge rule thus it does not change the dynamic of their missed field goals.