What you want to avoid is encryption or fingerprint use (or both?)?
To avoid encryption, (found here), you just can boot into recovery right after flashing, mount /dev/mapper/sailfish-root /mnt and delete /mnt/var/lib/sailfish-device-encryption/encrypt-home. I tried right now and it works.
If you only want to avoid fingerprint because your reader has a problem, can you not just skip the fp step at first boot?