Onyxcrowle, since all of these airports are private operations I dont think theyd take kindly to having their bread and butter flights moved to other airports. As far as I can tell, only LHR is severely constrained, and they dont have cargo flights as such due to the night time restrictions in place.
Market forces will continue to drive airports. MME is in a competitive market, and has the smallest core catchment out of its competitors. Hence the situation its in at the moment.