For instance the cervantes platform runs standalone with just
https://github.com/koreader/koreader...-standalone.sh.
But that's because we don't touch there the rest of the init scripts, so udev/mdev and a few other things (like running the agetty service that lets you login on the serial console) are still system code. Even then the script contains a fallback path, in case something went wrong during an update, to let you recover with either usbnet or usb mass storage.
You should do the same on your kobo, if you go that route.