Sorry for the late reply. Thank you both for your comments, at least I wasn’t overlooking something simple. My solution at this time was to flash a copy of the LEDE firmware onto one of my little Gl-iNet routers which connects to the EM7455 and communicates with it over MBIM. I use this setup as a gateway ‘device’ for the WAN on my pfSense box. This setup has been rock solid and I’ve only had to reset it once or twice since I’ve had it up and running.
It looks like the latest pfSense release has added a package for cellular connectivity drivers but it seems to be just Huawei devices for now (and no mention of MBIM or QMI so regardless, not worth running over PPP anyways). Eventually it would be nice to have everything running on the pfSense box (Gl-iNet has the limitation of 10/100 LAN so it is a slight bottleneck given the faster LTE speeds now available to my area) but my setup is fine for now. I will keep an eye on umb.4 for OpenBSD, maybe that will make it’s way into FreeBSD or I will someday spend the time getting the package into it myself, but I am okay with things as they are presently (‘if it works, don’t fix it’, as they say).