Comment # 4 on bug 906448 from Thomas Blume

(In reply to Christian Boltz from comment #3)
> Thomas, systemd-sysv-convert is _not_ about "rewriting" initscripts to a
> *.service file - while that would be nice, it's probably next to impossible
> to implement because the *.service files are more restricted and structured
> than the old initscripts (which basically allow to do anything).
> 
> systemd-sysv-convert is meant to help when a package replaces its initscript
> with a service file - it checks if the initscript was enabled, and if yes,
> activates the service. And that doesn't work for boot.* initscripts.

Ok, thanks for the background.
Indeed, the script only seems to support runlevels 2 to 5:

-->--
                if [ $runlevel -lt 2 -o $runlevel -gt 5 ]; then
                        echo "Runlevel out of bounds in database line $k.
Ignoring" >/dev/stderr
                        continue
                fi
[...]
        --save)
                shift
                for service in $@ ; do
                        if [ ! -r "/etc/init.d/$service" ]; then
                                echo "SysV service $service does not exist"
>/dev/stderr
                                exit 1
                        fi
                        for runlevel in 2 3 4 5; do
                                find_service $service $runlevel
                                priority=$?
                                if [ $priority -lt 255 ]; then
                                        echo "$service  $runlevel      
$priority" >> /var/lib/systemd/sysv-convert/database
                                fi
                        done
                done
--<--

The question is, do we have a target at all that is similar to the boot.*
scripts runlevel?
If systemd doesn't support this runlevel, I guess we don't.