Exactly, in cases which affect the system's behaviour due to serious changes like here, I would install a completely new realease, like you've done it with iso from 18th August.
Also here in forum there was asked how to change from sysvinit to systemd on a running system, but there occurred problems sometimes.
I think, a new release, prepared for using systemd as main init system, is more optimized for that new topic and it will prevent the problems which have occurred to some of our members here.
-Linuxfluesterer (I love KDE ...)
I really hope, that by the Brexit (poor Britain), TTIP will be finally prevented. But don't get tired to talk to your local politician to open eyes for danger to democracy because of TTIP