That was discussed on SME mailing list some years ago:
The goal here is to have a single growing partition. The best choice seems to be /var, as described by the FHS document, considering also that /var is the home directory prefix for system daemons
http://lists.contribs.org/pipermail/devinfo/2013-May/011702.html
It’s possible to map /home to /var/lib/nethserver/home by passing --bind option to the mount command, as @giacomo suggested here: