Severus considered that. "So, you suggest that Gringotts is lying?" A Potter descendant unrelated to Lily would not be particularly interesting to him, except inasmuch as he would be inclined to kill it, but the potential problem of the goblin bank becoming rebellious was interesting. If his purpose could not be to teach (he still got less than half as many NEWT students as Minerva and Filius), could not be to protect (plotting and planning and sneaking around, but protecting was Dumbledore's job), perhaps it could still be to fight.