I think these appointments are 'representational', rather than substantive and they have other jobs, which pay the rent. If not the RAF will be moving back to the 'Area' concept they had before 1936/7. On the face of it, there seems to be room for a lot of treading on toes and plenty of jobs for outer offices, ADCs etc. The precedent might be things like AO Wales, AO Scotland, AO Northern Ireland, which I think are filled by 'retired' officers.
As to Gerry Mayhew, this might be an early step to announcing the appointment of the next CAS.
Old Duffer