What would be wrong with reducing power on the "HD" signal at night on more powerful AMs? If the equiv. of a 5k station or so was used on all stations more powerful than 5k, let's say, at night, wouldn't that help prevent a lot of the issues people are legitimately conserned with? In most cases I'd think the main service area would be quite properly served which is what everyone seems to be concerned about anyway without causing a wall of skywave mush.