You are correct. A member of Parliament can speak with the PBO and have something included in the annual work plan, so in making the case to the PBO with the changes, I believe you could do it both at the beginning of the year in the establishment of the work plan, but also throughout the year so he could adjust his work plan throughout the year.
Another approach is in committee, so convincing the committee that this is an area of priority.
The third way is the amendment you're looking at now.