Hi Today, we introducing SamFw FRP Tool version 4.9 Main function: Remove FRP with one click Change CSC with one click Remove FRP for new secu...
samfw.com
This tool will allow you to check which CSC's are included in the OWO multi.
You can then look up each of those, and see if any of them have the firmware you want already.
The same tool can switch between the available CSCs, without root, or reinstall. Just a reboot.
That said, ZTO carrier configs existed in the XSA(OXM) stock firmware that I installed BR on. You could hypothetically use any G985F firmware. You won't get OTA updates. But you won't with BR anyway. Worst case might be your phone is in the wrong language...
But only do what you are comfortable with. It might not be worth the effort just to get a security patch a little sooner. Everything since FVDB still uses FVDB baseband. They are only security patches.