re air ride, i've owned older Mercedes wagons with hydropneumatic rear suspension, and a newer one with airmatic. The Hydropneumatic used a hydraulic fluid pump stacked on the power steering pump, a leveling valve attached to the rear suspension, hydraulic 'shocks' and nitrogen spheres to complete the rear suspension, based on the old Citroen system... Those rode really smoothly over all sorts of rough stuff. Same era, Mercedes had 4 wheel hydropneumatic, which was even better, on some of their larger luxury cars. As long as you flushed and changed the CHM hydraulic fluid every 10 years or so, those systems tended to work for the life of the chassis (which, on an S124 estate, was quite a long life). The more recent airmatic version, the air 'shocks' tend to wear out and spring leaks after 10 or so years, and while they do level the ride nicely, they don't really have that magic carpet ride of the old 1990 vintage Benzes.
of course, none of that relates to CCD but that has its own bunch of issues. I've heard/read that GMC's Air Ride Adaptive Suspension is better, but has its own issues.