Wouldn't that hang below the pan and decrease your clearance and put something really vulnerable there to get hit if you do run over a curb or something?
I can see why one might want a quick drain valve, but removing the filter makes a big enough mess already that you aren't saving time and mess by having one.
In thinking about this a bit, it might be ok on the 10+ models as their drain bolt location has changed to the side of the pan facing forward. Don't know how much the valve would stick down past the pan, though.