I know it's a loaded question and that there are trade-offs to consider in every decision. But you must agree that since the mains carry so much bass, their placement and the perfomance that results is is an important aspect, maybe even more so than the subs. In your proposed configuration, the most troublesome room modes for most people will fall in frequency ranges covered by the mains, not the subs. Would you place midbass cabinets randomly around the room, same as you suggest for subs?