[vezzy-fnord]

Hotplug isn't the job of systemd to begin with, though. It's the job of the device manager, which on Linux is usually udev (but alternatives like eudev, mdev, smdev and vdev exist) - udev being a part of the systemd repository and to an extent coupled with it (which will become complete when kdbus is merged into mainline Linux), however it's still a rather distinct piece of software that maintains the hardware database and listens to kernel uevents.

So if your init system is handling hotplug events, then that's some bad design. systemd doesn't stoop that low, though it still has plenty of mistakes - like putting the INI parser in PID1. As an example, even Apple put launchd's XML parser as a separate process!

[digi_owl]

There is tight interaction between udev and systemd. Heck, udev was folded into the systemd code (you find it now as a sub-dir of the systemd source tree over at freedesktop.org) because they didn't want code duplication...

This after having udev exist as a independent project for a decade.

These days the only way to download and install udev manually is to download the whole of systemd and then extract udev from that. Something that caused Gentoo to fork udev into eudev.