Foi mais fácil do que eu pensava, apenas instalar o pacote systemd-sysv
fez todas as alterações necessárias:
Breaks: sysvinit-core
Description-en: system and service manager - SysV links
systemd is a replacement for sysvinit. It is dependency-based and able to read the LSB init script headers in addition to parsing rcN.d links as hints.It also provides process supervision using cgroups and the ability to not only depend on other init script being started, but also availability of a given mount point or dbus service.
This package provides the manual pages and links needed for systemd to replace sysvinit.
Removeu o binário sysvinit (removendo o sysvinit-core) e substituiu /sbin/init
por um link simbólico para /lib/systemd/systemd