I am not so sure that the 'savings' to be made by chopping ...
Training Schools (police)
Driver Training
IT
Comms
Various Admin Depts (pay, personnel, crime management, stats etc)
not to mention the savings on 3 Chief Constables cars.. ha.!
are not illusions.
Training schools tend to be shared anyway, its odds on the IT will conflict from area to area and there will be a call to spend a way out of it.
I accept that on comms the ever so expensive new Tetra radio system should help out but with the record of the current Government getting the body count down in the various duplicate departments may not be realised.
As for the demise of Chief Constables, they are the ones under greatest threat and are fighting this as ACPO see themselves as having to survive as an organisation. If they do not they will be faced with having their annual conference in a phone box and not at Excel!
I can see you will get the 'spare' CC's cars allotted to the additional ACC's and DCC's required to undertake the workload.
And then there is the Police Authorities ... will they be reduced or will they evolve into local clones feeding an even larger entity? Regional PA's just like Regional Government!