I would like to propose that passing under a yellow flag be a 1 point penalty and a DQ from the qualifying session or race.

Being DQ'ed from the session and receiving a penalty point is enough of a penalty. A DQ and 2 points is excessive. Consider:

PCA: Drivers passing under yellow will be black flagged and assessed a stop and go penalty. If the infraction occurs on the last lap or two, and it is not possible to assess the stop and go penalty, the racer shall be penalized one lap.