Not sure why it should have to be MAS, BOND or Sloane.
What about Hems, Devon and Cornwall police and the MET?
They all appear to operate successfully as stand alone operations.
You save on operating costs but you lose out on having to contract in pilots and aircraft if required to cover sickness (on both counts!!!!). However I bet that doesn't come free anyway.
I believe that dedicated crews and engineers brings benefits of their own which are not always obvious to those holding the purse strings.