Earlier quoted context omitted.
The anti-systemd-brigade only seems to be a small minority of Debian devs (though they're very loud, and very persistent), so I'm not sure it would have much effect on the project as a whole. If a fork would reduce the time spent arguing about the init system (which 99% of users don't care about), it could even prove beneficial for Debian. [It seems unlikely the fork would attract the critical mass of devs/users to s…
I'm not even "anti-systemd". I'm actually in the process of implementing systemd for the firmware of an embedded target in $dayjob because socket activation is actually a good idea and happened to work well when I played with it. But a switch to a different init system shouldn't break your system so badly that it no longer boots. And yet that's what happens if you rely on keyscript to unlock your drives in /etc/crypt…
cryptopts=source=/dev/,target=sdc5_crypt,keyscript=/lib/cryptsetup/scripts/passdev,key=/dev/:/somdir/root.key
Anf then in /etc/fstab use the /dev/mapper/ (sdc5_crypt in the example above) as the root device, as before.
Then you need to make sure the initramfs contains all the tools needed to support this (that was done automatically with /etc/crypttab, it's "manual" with the kernel option). To do this, add under /etc/initramfs-tools/hooks a script file to load what's needed in the initramfs: cryptsetup, passdev, the needed kernel module. You can roughly copy the existing /usr/share/initramfs-tools/hooks/cryptroot and simplify it.
I've seen other distro documenting the kernel approach instead of /etc/crypttab for the root filesystem. It may become the standard way in the future, and there's no reason it couldn't be fully automated. There's some coordination between several components so it may take a bit of time to converge to an accepted and supported way thought.