After calling Apple tech support, we were able to troubleshoot it to something involving AudioUnits. The clue to this was that FCP was kernel panicking during the splash screen launching process and specifically during its AudioUnit examination.
The temporary workaround is to move all AudioUnits (Library > Audio > Plug-ins > Components) to another folder, then launch FCP, and verify that it launches properly. It does for me.
Based on that, the kernel panic is probably due to a 3rd party plug-in conflict, which I will now have to troubleshoot meticulously by putting AU's back in the folder, in batches at a time, until I can figure out which one is causing the KP.
Updating this post for anyone else who gets caught in this situation.