As we already have GR Examiners they will probably remain, but why would anyone apply to do it in the future especially if you have to pay a fee for the priviledge? I think some form of invigilation will be required but the thought of applying to be a GR just to invigilate is not realistic. It is an admin function which a DTO/ATO will provide to keep its customers in house.
Considering the original exam concept was to have one or two papers the practice of retaining nine seperate exams is simply clinging to the past with no real purpose. Once its all up and running it should prove more satisfactory and will illiminate the open exam papers left laying about and non qualified staff marking papers. One centre per airfield might be a reasonable target.