I saw in config.h that there is already the idea of defining "PISERVER_DATADIR" but I think it's not already finished. (finding very often hard-coded "/var/lib/piserver". It would be great to have this feature realized because it could improve security aspects by moving all data's to a crypted place (device, folder, img ...)
I'm also wondering why my work-around does not work:
mount -o bind /mnt/crypt/piserver/ /var/lib/piserver/
or even
mount -o bind /mnt/crypt/var/ /var/
pi's don't start