Earlier quoted context omitted.
Just curious, have you ever used systemd and ran into a problem where your service file screwed up and you had yo read systemd's source code or are you making this up?
xl2tpd, still doesn't work. I actually had to try to figure out why, turns out systemd supercedes lsmod/modprobe etc; causing those programs to return 1 when invoked, there's no debug or anything so I was seriously weirded out. took me some time to figure out it was systemd. the firewall wrapper for iptables gives you an insecure default config and is hard to fix via config management "add a service that means port 3…
You should be laying down a base initial configuration at the time that the machine was provisioned. The basic example of this is the sudoers file. The default setup for Ubuntu/RHEL is different enough that it was causing problems and the solution was simple - force defaults.