Hey @douglaskbell – not sure how best to answer your question because we don’t have a clear idea of what you’re trying to accomplish.
If you want to use the Electron with a 3rd party cellular carrier, you don’t need to change anything in the firmware other than the APN. We have a flow that you can use at http://setup.particle.io that walks you through the process of generating firmware with another APN. You shouldn’t have to do anything else – the communication between the modem and SIM card is all handled by a firmware stack on the u-blox module and is written by u-blox.
If you want to use the Electron with a 3rd party cellular modem (non-ublox), then you would have to modify the Particle firmware base (in addition to redesigning the PCB). If you’re interested in porting Particle’s firmware stack to other hardware, then that’s a more complicated process.