A good comparison for the type of area that our local Police and Crime Commissioner covers (Devon and Cornwall) is South Wales. It also has a mix of large cities (Cardiff, Swansea), large and small towns and coastal and very rural areas. It has a similar number of police – 3,556 in Devon and Cornwall and 3,148 in South Wales.
Here our Commissioner needs a staff of 23 or 31 (depending on who is counting). In South Wales, their Commissioner manages on a staff of 16, including the Commissioner.