Originally Posted by Red Bread
MB does frameless windows on many of their cars without such a thick b-pillar. Having driven a few rental sedans with thick b-pillars, I find it to be a terrible blind spot, as it's right where I look when looking over my shoulder. Regardless, this whole class of car, CLS, A7, A5 Sportback is generally pretty ugly in my opinon, the 6 GT being the first car in the class that I like (at least in pictures, I haven't seen one in person yet).
I know MB does frameless windows with thinner B pillars, in some case without any B pillar of any kind.
BMW on the other hand like their thick B pillars. They did the same thing with the previous 6 Series, apparently the reason being to keep the body as rigid as possible.
I understand your point about it causing problems if you look over your shoulder (I suspect when changing lanes?). I have more or less the same problem with the ever increasing sloped front windscreens of modern cars where the A pillars cause blindspots in your forward field of vision, but that's probably beside the point.
I doubt the B pillars in this case are significantly wider than what you'd find on a normal 4-door E90 for instance. I could be completely wrong, but I think it just looks wider because of the frameless windows.
EDIT: Probably worth noting that manufacturers could probably get away without a B pillar in a coupe body design, but in a 4-door design (like this), the roof is quite a bit longer. I sincerely doubt you'd see a design without a B pillar of some sort on modern 4 door cars, and if you do, it would probably handle like a French Fry.
Whatever the case may be, I completely agree with you about the new 4-door-that's-based-on-the-2-door-that's-based-on-the-4-door madness currently going on. Sure new niches may sell up a storm, but we don't have to like it.