I would still wait until someone has done this before expecting that it can work. I have purchased unrestricted international 1st tickets ( which by default allow unlimited free changes ) however making a change to the initial flight has caused a need for recalculation of fare and , when there has been a price rise, payment of the difference

Although free changes may be permitted on the OWEs , I would not be convinced that the suggested workaround would work if the initial departure date changes.

Dave