Is it possible for a python script to run against the offline replicas that Collector stores for a disconnected device? I've got data being collected in the field by disconnected devices and to change the symbology based on that data in real-time would be nice.
As far as using Arcpy on a mobile device, no its not possible as it depends on the .dlls installed by Desktop or Server to work. You may be able to achieve what you want however by adding metadata fields and deriving the symbology from those https://doc.arcgis.com/en/collector/ios/create-maps/gps-map-prep.htm