This python module allows you to define a take a geofence defined by GPS coordinates contained in a KML/KMZ file and resize this geofence proportionally. This will work regardless of the geofences complexity, however this software does not yet have the capability to merge points that will overlap as you resize the geofence.
Francesco-Lanciana/geofence
A module that enables you to resize a geofence of any size and complexity
Python