LAVA, until now, has packaged SysVinit files to manage the various daemons but there have been longstanding problems with log rotation and the need to carry redundant code to manage the daemonize process for python scripts. This has allowed instances to support both SysVinit and systemd because systemd automatically converts the SysVinit files to systemd service files.
Now that V1 has been removed, it has become possible and advantageous to drop SysVinit support and move to only systemd support. This is expected to mean that lava-dispatcher (and therefore lava-server) will depend on systemd-sysv, i.e. systemd needs to be the init system to be able to start the daemons upon which LAVA relies.
A default install of Debian Jessie and Stretch already defaults to using systemd as the init system, so this does not necessarily involve any changes.
If there are questions or issues with this, please reply to the lava-users mailing list.