I agree with most of your points in your post. I cannot stress enough that a lightweight cone will out perform a heavy weight cone and suspension design.
Examples: Older JL audio, SoundStream, PG Titanium, Eclipse Ti, etc. These subs have lighter cones and suspensions and sound more "clear"/clean with lower power requirements.
Have you ever seen the cone distortion videos on Youtube that show cones flexing and flapping all over the place in slow motion? Some is bad videography, others are using good quality cameras and documenting the visible distortion in the cone. This distortion comes from high motor force that's required to control the heavier cone or overcome stiff suspension.
Examples: DC Audio, FI BTL, possibly some DD 9500 or higher series.
Better motor control, split coils, etc definitely help reduce introducing distortion. A well designed motor does not have to be so strong as it must be linear throughout the excursion. Examples of bad motor designs would be the double-stacked DD motors or other smaller motors with all of the motor force in the center of the coil travel. Very little control outside of the "sweet spot" in the BL curve.
The home audio and pro audio speakers I was referring to are component type speakers. mostly 3-way, in a single cabinet. I have also heard very good sounding Polk audio 2-way tower speakers that had a 30-20K range, right at ear level. The subwoofer LPF was tuned to 50hz. All of these higher end speakers used reinforced paper, not poly or aluminum cones.
I think we're on the same page, so I don't want to beat a dead horse any longer. Just saying that I believe there is a lot more to do with speaker design in the cone and suspension than most people give merit to.