Re: I've forgotten...
I've never had a problem using the old System V method which was decades-stable
SysV scripts can be a little intimidating at first; you'll notice that the systemd-proponents seem to like to make a fuss about how many lines they are. But that length is a strength, IMO, not a weakness; you have the operation of the script laid out explicitly for your examination, rather than hidden within an executable. SysV scripts are very debuggable, and trivially modified if you want *your* box to do something different to what the package maintainer wanted.
Now I daresay that much or all of what I want to do is possible within systemd - but that involves learning another control system. I already know Bourne-shell scripting - I think it's pretty much certain that any successful *nix admin will - so all we're really doing here is taking an easily-readable, debuggable script written in a language I understand well and replacing it with a configuration file for an executable I don't know and can't readily inspect. That's obfuscation.
I've also never seen network adaptors 'reverse' (and I run multi-home machines, so there)
I have when you change the physical hardware. I'm not sure I really know how to identify a particular card except by its PCI position (fragile) or its MAC address (somewhat more resilient).
The former could probably be done with udev or similar (I've never done it, and never expect to, since it's a horrible way of doing things). The latter is trivial. I can't actually think of a third way...