I started a similiar thread:
https://forum.openwrt.org/t/pi-sim-card-4g-lte-modem-firmware/55366
My motivation for no wifi and no battery is to prevent the ISP from labeling it as a "Mobile Hotspot".
The thread has 2 links that show the build on a Rasberry Pi3.
If you have other reasons for no wifi, most routers allow you to disable it.