Well, BMW and Mercedes must be different from Premium brands (as Audi or Lexus). It's their only advantage (they don't have mass-market resources).
Their technology is one step above Premium brands, now it's necessary to show the difference also to the eye and touch.
Mercedes is already on the task.
They're going to divide the brand into two parts.
Luxury cars from C-class and above.
Premium FWD with A, B class, the SUV, CLA 4 door coupe and similar variants.
The new 2014 C-class is not only getting much longer, the interior will remind heavily on the new 2013 S-class interior. The new C-class is going to become a mini S-class; a perfect Mercedes brand-perception solution.
BMW 3 series has a history of its own and a similar idea would be terrible.
Some ten years ago there was an article in a German newspaper, where the BMW CEO at the time said, that BMW was never as long as Mercedes cars and is not going to follow in Mercedes wake.
Now look at the 3 series.
The E36 (year 1991) was 4433mm long, had a 2.700mm long wheelbase (BMW 1series today) and it's interior width was 1.425mm (from driver to co-driver doors).
The new 3 series is 4.624mm long, with a 2.810mm long wheelbase.
The interior width has gone from 1.425mm to 1.451mm; only +2,6cm
I understand that BMW could not ignore the competition and not make it's car longer. The new 3 series in now perfect also for rear passengers. No problem.
However, offering the same cramped narrow interior-width of 20 years ago???
Even a one step lower compact car like Audi A3 offers significantly more elbow room.
The idea of making a 2er Gran Coupe is great.
A revival of the E36 would be marvelous; a much better idea that the CLA that is only Premium (FWD) and is not looking that good in final serial version.
However, if the interior remains as wide as in a sub-compact mass-market car, even the BMW technical content is not going to be enough to make the car stand apart from Audi A3 sedan and Mercedes CLA.