We have developed a simulation module (UNISEMS) that can integrate with Ignition directly thru a GCM module or thru OPC-UA (you will have to expose all tags thru OPC UA interface for this). However the simulation models will have to be written in GNU FORTRAN. See Introduction and Demo of UNISEMS. of UNISEMS module.
As you are writing your simulator in Python , UNISEMS will have to be slightly modified to suit your requirements.