With Chilterns service in mind, if I were the planners, I would remove the whole Amersham service and still run 2tph on Chesham service.
Only passengers at Amersham will lose out service by needing to change at Chalfont or Rickmansworth
There isn’t really any benefit to doing so, particularly this time round. The drivers will all be available, and the rolling stock situation shouldn’t be so dire as two trains will make a difference. Additionally, the Chesham trains remain in their standard path north of Rickmansworth, placing them three minutes in front of northbound Chilterns and five minutes behind on the south. Most importantly, though, the trains add much needed capacity south of Harrow, and help to provide a reasonably even 5 minute headway (approx 12tph).
It should also be noted that this timetable has been developed by the local Met Service Control team, and has proved extremely robust - much more so than that provided by LU Schedules - whenever it has been used over the last two years.