[Shujin]

Sancity is quite the useless stat for them actually, cause you need to spend points in it that are simply better spend somewhere else.
Most races don´t only get the bonus from San itself but racial bonuses, making a single point in SAN alot more useful to them, and it´s still hard to build a valid SAN cahracter outside of Vampires.

If not sancity, maybe we just go similiar route as suggested in OP just with Scaled APT/6 or something? That would make humans decent...They need the extra class points kinda to make up for their lack of racials and immunities certain races have.