-1 here. I need to be able to carry bulky luggage equally comfortably on my back and on the bike. Panniers do not help. One way to solve it is to have one or both wheels small and have the luggage ride above the small tire, with center of mass close to the ground then.
Well, you might as well get a bakfiets then. My pannier/tailbox ends the dilemma of choosing between saddlebags, or placing the basket on top of the rack... by combining both in one.