@amadaluzia @catavz pf.conf.d ... could be a good idea, but you'd have to have priority numbers. ipfw just has those on the rules themselves; this seems like a more complete working out of the idea. That way your software can insert rules in different places while still having all its rules in one file. (although i don't know if ipfw.conf.d exists, or whatnot.)
More generally, though, this is changing the firewall under programmatic control, and that's part of the intrusion of dev into ops that's implicit in modern usage of the word "container." Hmm, so you... turn on multilevel jails, start a jail with a VNET behind a bridge, and run #podman in the jail, whereunder it starts child jails. podman gets a pf.conf to mess with, and you get a pf.conf it can't touch. :) or... what if someone makes a #CNI that uses #netgraph instead? hmmm