That's why I'm on board with allowing it. I feel that it is a play that is going to lead to a serious injury because of the "scrum" nature of it. But so far it has not, so why ban it based on a possible outcome?
I think with the hip-drop, enforcement needs to be very limited in scope. If a defender drops his weight onto the legs of the offensive player, then and only then should it be a penalty. And that appears to be what they are considering. Against bigger players, it is necessary for defenders to sometimes drop their weight to bring them down or otherwise just be dragged down the field. The main danger with the hip-drop is when the weight of a player is suddenly dropped on the back of another player's legs.