I agree here. Even experts here mention that part of AM's problem is that even stations in big metros have smaller signal footprints than the metro which outgrew them, and RFI is part of the problem on top of that. Signal strength over your primary area is important.
Perhaps it would be better to scrap the concepts of blowtorches and directional regionals, and focus on signal strength and pattern to serve the market? Eliminating Class A, B, C and D classifications and focusing on an allocation plan (similar to FM or TV) would be a start. Making sure that signal strength is just enough (to overcome RF interference and poor soils, but minimize skywave) and that the pattern serves the entire market would do wonders to revitalize AM radio.
But eliminating the MW service and going FM-only is much the simpler way to get things done!