The advantage is that the kernel panics if PID 1 ever crashes, so I want PID 1 never to crash or even be able to crash. It also means I want the binary to have as little of an attack surface as possible, and particularly I don't want it listening to dbus or having links to a QR generation library.
This is a solved problem with multiple good solutions [1] [2] [3], so I can easily avoid those issues by not using systemd.
So add a signal handler that just enters an endless loop. That's what systemd does, so as not to panic the kernel on a crash.
By the way, systemd doesn't listen to dbus (it uses the dbus protocol for IPC) and does not link to a QR generation library (journalctl does, which is your usual unprivileged program).
This is a solved problem with multiple good solutions [1] [2] [3], so I can easily avoid those issues by not using systemd.
[1] http://www.gnu.org.ua/software/pies/
[2] http://universe2.us/epoch.html
[3] http://core.suckless.org/sinit